JP7670100B2 - Semiconductor device and method for manufacturing the same - Google Patents

Description

The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device.

2. Description of the Related Art Conventionally, a technique for adjusting the doping concentration of a semiconductor wafer by implanting hydrogen ions into the semiconductor wafer has been known (see, for example, Japanese Patent Application Laid-Open No. 2003-233663).
Patent Document 1 US2015/0050754

Problem to be solved

It is preferable that hydrogen can easily diffuse to areas distant from the hydrogen injection site.

General Disclosure

In order to solve the above problem, one aspect of the present invention provides a semiconductor device including a semiconductor substrate having an upper surface and a lower surface and including a bulk donor. The semiconductor device may include a buffer region of a first conductivity type disposed on the lower surface side of the semiconductor substrate and having one or more doping concentration peaks in a depth direction of the semiconductor substrate. Any of the above semiconductor devices may include a high concentration region of a first conductivity type disposed between the buffer region and the upper surface of the semiconductor substrate and having a donor concentration higher than a bulk donor concentration . In any of the above semiconductor devices, the shallowest doping concentration peak of the doping concentration peaks in the buffer region and closest to the lower surface of the semiconductor substrate may be a concentration peak of a hydrogen donor having a higher concentration than the other doping concentration peaks. In any of the above semiconductor devices, a ratio β between an actual bulk donor concentration N _Bre (/cm ³ ) and a specified value N _B0 (/cm ³ ) of the bulk donor concentration is defined by the following formula:
β=N _Bre /N _B0
The ratio γ of the actual donor concentration N _Fre (/cm ³ ) in the high-concentration region to the target value N _F0 (/cm ³ ) of the donor concentration in the high-concentration region is defined by the following formula:
γ=N _Fre /N _F0
A parameter ε′, which means that the specification value N _B0 of the bulk donor concentration is set to be smaller than the target value N _F0 of the donor concentration by ε′, is defined by the following equation:
N _B0 = ε ' × N _F0
The relationship between the ratio β, the ratio γ, and the parameter ε′ is expressed by the following formula:
γ=1+ε′(β−1)
In the above formula, the value of the ratio β is 0.1 or more and 10 or less, the value of the ratio γ is 0.85 or more and 1.15 or less, and the value of the parameter ε′ is 0.001 or more and 0.5 or less,
The ratio γ may satisfy the above formula within the ranges of the ratio β, the ratio γ, and the parameter ε′.

In any of the above semiconductor devices, the semiconductor substrate may be an MCZ substrate.

In any one of the above semiconductor devices, when a rated voltage of the semiconductor device is x (V), the actual donor concentration N _Fre is (9.20245 x 10 ¹⁵ )/x or more, (9.20245×10 ¹⁶ )/x.

In any one of the above semiconductor devices, when the rated voltage of the semiconductor device is x (V), the actual bulk donor concentration N _Bre But (9.20245 x 10 ¹² )/x or more, (4.60123×10 ¹⁶ )/x or less.

Any of the above semiconductor devices may further include an impurity chemical concentration peak disposed on the upper surface side of the semiconductor substrate. In any of the above semiconductor devices, the high concentration region may include a uniform region having a substantially uniform doping concentration. In any of the above semiconductor devices, the doping concentration distribution of the uniform region may have a doping concentration distribution value within ±50% of an average concentration of the doping concentration distribution in a first range. In any of the above semiconductor devices, the first range may be a length of the high concentration region in the depth direction that is Z _L The center between the shallowest doping concentration peak and the impurity chemical concentration peak in the depth direction is Z _12c In this case, the center Z _12c Including 0.5Z _L The interval may be an interval of length .

Any of the above semiconductor devices may further include an impurity chemical concentration peak disposed on the upper surface side of the semiconductor substrate. In any of the above semiconductor devices, an upper base where the impurity chemical concentration decreases from the apex of the impurity chemical concentration peak toward the upper surface side may decrease more steeply than a lower base where the impurity chemical concentration decreases from the apex of the impurity chemical concentration peak toward the lower surface side. In any of the above semiconductor devices, the buffer region may have two or more of the doping concentration peaks.

In order to solve the above problems, in another aspect of the present invention, a bulk donor concentration specification value N _B0 (/cm ³ The method for manufacturing a semiconductor device further comprises a step of determining a target value N _F0 (/cm ³ Any of the above-mentioned methods for manufacturing a semiconductor device may include a first implantation step of implanting charged particles and hydrogen ions from an upper surface or a lower surface of the semiconductor substrate. Any of the above-mentioned methods for manufacturing a semiconductor device may include a first annealing step of annealing the semiconductor substrate. In any of the above-mentioned methods for manufacturing a semiconductor device, the hydrogen donor concentration by the implantation of the hydrogen ions may be determined as N _H (/cm ³ ) and the actual bulk donor concentration of the semiconductor substrate is N _Bre (/cm ³ ) and the final donor concentration actually obtained in the semiconductor substrate is N _Fre (/cm ³ ), the target value of the donor concentration N _F0 is the specified value of the bulk donor concentration N _B0 and the hydrogen donor concentration N _H Therefore, N _F0 = N _H +N _B0 and the final donor concentration N _Fre is the actual bulk donor concentration N _Bre and the hydrogen donor concentration N _H Therefore, N _Fre = N _H +N _Bre and the actual bulk donor concentration N _Bre and the bulk donor concentration specification value N _B0 The ratio β is defined as follows:
β=N _Bre /N _B0
The actual donor concentration N _Fre and the target value N of the donor concentration _F0 The ratio γ is defined as follows:
γ=N _Fre /N _F0
The target value N of the donor concentration _F0 , the bulk donor concentration specification value N _B0 The parameter ε', which means to set the value of the parameter ε' to be smaller than the value of the parameter ε', is defined as follows:
N _B0 = ε' × N _F0
The relationship between the ratio β, the ratio γ, and the parameter ε′ is expressed by the following formula:
γ=1+ε'(β-1)
In the above formula, the value of the ratio β is 0.1 or more and 10 or less, the value of the ratio γ is 0.85 or more and 1.15 or less, and the value of the parameter ε' is 0.001 or more and 0.5 or less, and the first implantation step and the first annealing step may be performed so that the ratio γ satisfies the above formula within the ranges of the values of the ratio β, the ratio γ, and the parameter ε'.

In any of the above methods for manufacturing a semiconductor device, the semiconductor substrate may be an MCZ substrate.

In any one of the above-described methods for manufacturing a semiconductor device, when a rated voltage of the semiconductor device is x (V), the final donor concentration N _Fre is (9.20245 x 10 ¹⁵ )/x or more, (9.20245×10 ¹⁶ )/x.

In any one of the above-mentioned methods for manufacturing a semiconductor device, when a rated voltage of the semiconductor device is x (V), the actual bulk donor concentration N _Bre But (9.20245 x 10 ¹² )/x or more, (4.60123×10 ¹⁶ )/x or less.

In any of the above-described methods for manufacturing a semiconductor device, in the first implantation step, the hydrogen ions may be implanted from the lower surface to a first position, and the charged particles may be implanted to a second position closer to the upper surface of the semiconductor substrate than the first position.

In any of the above methods for manufacturing a semiconductor device, the second position may be disposed on the upper surface side of the semiconductor substrate.

In the first annealing step of any of the above methods for manufacturing a semiconductor device, a high concentration region having a donor concentration higher than the bulk donor concentration may be formed in the semiconductor substrate from the first position to the second position.

In any of the above methods for manufacturing a semiconductor device, the high concentration region may include a uniform region having a substantially uniform doping concentration. In any of the above methods for manufacturing a semiconductor device, the doping concentration distribution of the uniform region may have a doping concentration distribution value within ±50% of an average concentration of the doping concentration distribution in a first range. In any of the above methods for manufacturing a semiconductor device, the first range may be a depth direction length of the high concentration region within Z _L and the center between the first position and the second position in the depth direction is Z _12c In this case, the center Z _12c Including 0.5Z _L The interval may be an interval of length .

Note that the above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions.

1A to 1C are cross-sectional views showing an example of a method for manufacturing the semiconductor device 100. 1. The distributions of the lattice defect density D _V , hydrogen chemical concentration C _H , doping concentration D _d and impurity chemical concentration C _I in the depth direction at the position indicated by the line AA in FIG. 1 are shown. 1 shows the distributions of the lattice defect density D _V , the hydrogen chemical concentration C _H , the doping concentration D _d and the impurity chemical concentration C _I according to the comparative example. FIG. 2 shows the distribution of hydrogen chemical concentration C _H and doping concentration D _d in the vicinity of the buffer region 20. 4 is a flowchart showing an example of a manufacturing method of the semiconductor device 100. 10 is a flowchart showing another example of the method for manufacturing the semiconductor device 100. 10 is a flowchart showing another example of the method for manufacturing the semiconductor device 100. 10 is a flowchart showing another example of the method for manufacturing the semiconductor device 100. FIG. 13 is a diagram showing an example of the distribution of hydrogen chemical concentration _CH in the vicinity of the buffer region 20. 13 is a diagram showing a change in doping concentration _Dd in the vicinity of the buffer region 20 when the dose of hydrogen ions at the first depth position Z1 is changed. FIG. FIG. 1 is a diagram for explaining the relationship between a hydrogen chemical concentration peak 131-1 and a doping concentration peak 111-1. 1 is a diagram illustrating the relationship between an impurity chemical concentration peak 141 and a doping concentration peak 121. FIG. 13 is a diagram illustrating the inclination of a lower hem 142. FIG. 13 is a diagram illustrating another definition of the normalization of the slope of the lower skirt 112. FIG. 13 is a diagram illustrating another definition of the normalization of the slope of the lower skirt 122. FIG. 1 is a graph showing the relationship between ε′ and γ shown in equation (12) for each β. FIG. 13 is a diagram showing an example of a preferred range of bulk donor concentration N _Bre . FIG. 13 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε′ is in the range B (0.01 or more and 0.333 or less). FIG. 13 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε′ is in the range C (0.03 or more and 0.25 or less). FIG. 13 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε′ is in the range D (0.1 or more and 0.2 or less). FIG. 13 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε′ is in the range E (0.001 or more and 0.1 or less). FIG. 13 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε′ is in the range F (not less than 0.002 and not more than 0.05). FIG. 13 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε′ is in the range G (not less than 0.005 and not more than 0.02). FIG. 13 is a diagram showing an example of a preferred range of bulk donor concentration N _Bre when ε′ is in the range H (0.01±0.002). FIG. 2 is an example of a top view of the semiconductor device 100. FIG. 21 is an enlarged view of area A in FIG. 20 . 22 is a diagram showing an example of the bb cross section in FIG. 21. FIG. 22B is a diagram showing an example of distribution of doping concentration _Dd along line dd in FIG. 22A. FIG. 22 is a diagram showing another example of the bb cross section in FIG. 21.

The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

In this specification, one side in a direction parallel to the depth direction of the semiconductor substrate is referred to as "upper" and the other side as "lower." Of the two main surfaces of a substrate, layer, or other member, one surface is referred to as the upper surface and the other surface is referred to as the lower surface. The directions of "upper" and "lower" are not limited to the direction of gravity or the directions when the semiconductor device is mounted.

In this specification, technical matters may be explained using the orthogonal coordinate axes of the X-axis, Y-axis, and Z-axis. The orthogonal coordinate axes merely identify the relative positions of components, and do not limit a specific direction. For example, the Z-axis does not limit the height direction relative to the ground. Note that the +Z-axis direction and the -Z-axis direction are opposite directions. When the Z-axis direction is described without indicating positive or negative, it means the direction parallel to the +Z-axis and -Z-axis.

In this specification, the orthogonal axes parallel to the upper and lower surfaces of the semiconductor substrate are referred to as the X-axis and Y-axis. The axis perpendicular to the upper and lower surfaces of the semiconductor substrate is referred to as the Z-axis. In this specification, the direction of the Z-axis may be referred to as the depth direction. In this specification, the direction parallel to the upper and lower surfaces of the semiconductor substrate, including the X-axis and Y-axis, may be referred to as the horizontal direction.

The region from the center of the semiconductor substrate in the depth direction to the upper surface of the semiconductor substrate may be referred to as the upper surface side. Similarly, the region from the center of the semiconductor substrate in the depth direction to the lower surface of the semiconductor substrate may be referred to as the lower surface side. In this specification, the center position of the semiconductor substrate in the depth direction may be referred to as Zc.

When terms such as "same" or "equal" are used in this specification, this may include cases in which there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

In this specification, the conductivity type of a doped region doped with impurities is described as P type or N type. In this specification, impurities may specifically mean either N type donors or P type acceptors, and may be described as dopants. In this specification, doping means introducing donors or acceptors into a semiconductor substrate to make it a semiconductor that exhibits N type conductivity or a semiconductor that exhibits P type conductivity.

In this specification, the doping concentration means the concentration of the donor or the concentration of the acceptor in a thermal equilibrium state. In this specification, the net doping concentration means the net concentration obtained by adding up the donor concentration as the concentration of positive ions and the acceptor concentration as the concentration of negative ions, including the polarity of the charge. As an example, if the donor concentration is N _D and the acceptor concentration is N _A , the net doping concentration at any position is N _D -N _A. In this specification, the net doping concentration may be simply referred to as the doping concentration.

A donor has the function of supplying electrons to a semiconductor. An acceptor has the function of receiving electrons from a semiconductor. Donors and acceptors are not limited to impurities themselves. For example, a VOH defect in a semiconductor, which is a combination of a vacancy (V), oxygen (O), and hydrogen (H), functions as a donor that supplies electrons. In this specification, a VOH defect may be referred to as a hydrogen donor.

In this specification, when it is written P+ type or N+ type, it means that the doping concentration is higher than that of P type or N type, and when it is written P- type or N- type, it means that the doping concentration is lower than that of P type or N type. Also, when it is written P++ type or N++ type, it means that the doping concentration is higher than that of P+ type or N+ type. The unit system in this specification is the SI unit system unless otherwise specified. The unit of length may be expressed in cm, but various calculations may be performed after converting to meters (m).

In this specification, chemical concentration refers to the atomic density of an impurity measured regardless of the state of electrical activation. The chemical concentration (atomic density) can be measured, for example, by secondary ion mass spectrometry (SIMS). The above-mentioned net doping concentration can be measured by a voltage-capacitance measurement method (CV method). The carrier concentration measured by a spreading resistance measurement method (SR method) may be the net doping concentration. The carrier concentration measured by the CV method or the SR method may be a value in a thermal equilibrium state. In addition, since the donor concentration is sufficiently larger than the acceptor concentration in an N-type region, the carrier concentration in that region may be the donor concentration. Similarly, in a P-type region, the carrier concentration in that region may be the acceptor concentration. In this specification, the doping concentration in an N-type region may be referred to as the donor concentration, and the doping concentration in a P-type region may be referred to as the acceptor concentration.

Furthermore, when the concentration distribution of the donor, acceptor or net doping has a peak, the peak value may be taken as the concentration of the donor, acceptor or net doping in the region. When the concentration of the donor, acceptor or net doping is almost uniform, the average value of the concentration of the donor, acceptor or net doping in the region may be taken as the concentration of the donor, acceptor or net doping. In this specification, atoms/cm ³ or /cm ³ may be used to express concentration per unit volume. This unit is used for donor or acceptor concentration or chemical concentration in a semiconductor substrate. The notation of atoms may be omitted.

The carrier concentration measured by the SR method may be lower than the donor or acceptor concentration. In the range where current flows when measuring the spreading resistance, the carrier mobility of the semiconductor substrate may be lower than the value in the crystalline state. The reduction in carrier mobility occurs when the carriers are scattered due to disorder in the crystal structure caused by lattice defects, etc.

The donor or acceptor concentration calculated from the carrier concentration measured by the CV method or the SR method may be lower than the chemical concentration of the element representing the donor or acceptor. As an example, the donor concentration of phosphorus or arsenic, which acts as a donor in a silicon semiconductor, or the acceptor concentration of boron, which acts as an acceptor, is about 99% of the chemical concentration. On the other hand, the donor concentration of hydrogen, which acts as a donor in a silicon semiconductor, is about 0.1% to 10% of the chemical concentration of hydrogen. The concentrations in this specification may be values at room temperature. As an example, values at 300 K (Kelvin) (about 26.9° C.) may be used as the values at room temperature.

When charged particles such as ions or electrons are implanted into a semiconductor substrate with a predetermined acceleration energy, these particles have a predetermined distribution in the depth direction. In this specification, the peak position of the distribution may be referred to as the position where the particles are implanted, the implantation depth, etc.

Figure 1 is a cross-sectional view showing an example of a manufacturing method for a semiconductor device 100. The semiconductor device 100 includes a semiconductor substrate 10. The semiconductor substrate 10 is a substrate formed of a semiconductor material. As an example, the semiconductor substrate 10 is a silicon substrate.

At least one of a transistor element such as an insulated gate bipolar transistor (IGBT) and a diode element such as a free wheel diode (FWD) is formed on the semiconductor substrate 10. In FIG. 1, the electrodes of the transistor element and the diode element and the regions provided inside the semiconductor substrate 10 are omitted. Configuration examples of the transistor element and the diode element will be described later.

In the semiconductor substrate 10 of this example, N-type bulk donors are distributed throughout. The bulk donors are donors due to dopants that are contained almost uniformly in the ingot when the ingot that is the base of the semiconductor substrate 10 is manufactured. The bulk donors in this example are elements other than hydrogen. The dopants of the bulk donors are, for example, phosphorus, antimony, arsenic, selenium, or sulfur, but are not limited thereto. The bulk donors in this example are phosphorus. The bulk donors are also contained in the P-type region. The semiconductor substrate 10 may be a wafer cut from a semiconductor ingot, or may be a chip obtained by dividing the wafer. The semiconductor ingot may be manufactured by any of the Czochralski method (CZ method), the magnetic field application type Czochralski method (MCZ method), and the float zone method (FZ method). The ingot in this example is manufactured by the MCZ method. The oxygen concentration contained in the substrate manufactured by the MCZ method is 1×10 ¹⁷ to 7×10 ¹⁷ /cm ^3. The oxygen concentration contained in the substrate manufactured by the FZ method is 1×10 ¹⁵ to 5×10 ¹⁶ /cm ^3. The higher the oxygen concentration, the easier it is for hydrogen donors to be generated. The bulk donor concentration may be the chemical concentration of the bulk donors distributed throughout the semiconductor substrate 10, and may be a value between 90% and 100% of the chemical concentration. The semiconductor substrate 10 may be a non-doped substrate that does not contain dopants such as phosphorus. In this case, the bulk donor concentration of the non-doped substrate is, for example, 1×10 ¹⁰ /cm ³ or more and 5×10 ¹² /cm ³ or less. The bulk donor concentration of the non-doped substrate is preferably 1×10 ¹¹ /cm ³ or more. The bulk donor concentration of the non-doped substrate is preferably 5×10 ¹² /cm ³ or less.

The semiconductor substrate 10 has an upper surface 21 and a lower surface 23. The upper surface 21 and the lower surface 23 are the two main surfaces of the semiconductor substrate 10. In this specification, the orthogonal axes in a plane parallel to the upper surface 21 and the lower surface 23 are the X-axis and the Y-axis, and the axis perpendicular to the upper surface 21 and the lower surface 23 is the Z-axis.

An N-type buffer region 20 is provided on the lower surface 23 side of the semiconductor substrate 10 (i.e., the region between the lower surface 23 and the center position Zc in the depth direction). A lower surface region 201 is provided between the buffer region 20 and the lower surface 23. The lower surface region 201 is an N-type or P-type region with a higher doping concentration than the high concentration region 150 described below. The lower surface region 201 may be a cathode region or a collector region described below. The buffer region 20 prevents a depletion layer spreading from the upper surface 21 side of the semiconductor substrate 10 from reaching the lower surface region 201 (punch-through).

The buffer region 20 has multiple doping concentration peaks 111 in the depth direction of the semiconductor substrate 10. In the example of FIG. 1, the buffer region 20 has doping concentration peaks 111-1, 111-2, 111-3, and 111-4, in that order from the bottom surface 23 side. By providing multiple doping concentration peaks 111, it is possible to prevent the above-mentioned depletion layer from spreading to the bottom surface region 201. In this specification, the doping concentration peak 111-1 may be referred to as the shallowest doping concentration peak. The doping concentration peak 111-1 has a higher doping concentration than the other doping concentration peaks 111. The buffer region 20 may contain a hydrogen donor.

In the manufacturing method of this example, the multiple doping concentration peaks of the buffer region 20 are formed in two stages. In the first stage S1001, charged particles are injected from the lower surface 23 of the semiconductor substrate 10 to the second depth position Z2. The charged particles are, for example, hydrogen ions, helium ions, electrons, etc. The semiconductor substrate 10 of this example has an impurity chemical concentration peak 141 of hydrogen or helium, etc., at the second depth position Z2. The second depth position Z2 may be a position above the upper surface 21. In other words, the charged particles may be injected so as to penetrate the semiconductor substrate 10.

The depth position is a position in the depth direction (Z-axis direction) of the semiconductor substrate 10. In this specification, the distance from the lower surface 23 to each position may be referred to as the depth position of each position. For example, the second depth position Z2 has a distance Z2 from the lower surface 23. The second depth position Z2 may be located on the upper surface 21 side of the semiconductor substrate 10 (i.e., the region between the upper surface 21 and the center position Zc in the depth direction).

The average distance (also called the range) that the charged particles travel inside the semiconductor substrate 10 can be controlled by the acceleration energy that accelerates the charged particles. In this example, the acceleration energy is set so that the average range of the charged particles is distance Z2. The average range Z2 of the charged particles may be greater than half the thickness of the semiconductor substrate 10 in the depth direction.

In this specification, the region through which the injected charged particles pass may be referred to as the passing region 106. In the example of FIG. 1, the passing region 106 is from the lower surface 23 of the semiconductor substrate 10 to the second depth position Z2. In the example of FIG. 1, the charged particles are injected from the entire lower surface 23 of the semiconductor substrate 10. In another example, the charged particles may be injected into only a partial region of the lower surface 23. This allows the passing region 106 to be formed locally in the XY plane.

In the first step S1001, hydrogen ions such as protons are implanted from the lower surface 23 of the semiconductor substrate 10 to a first depth position Z1. After the hydrogen ions are implanted, the entire semiconductor substrate 10 is annealed. As a result, a doping concentration peak 111-1 due to hydrogen donors is formed at the first depth position Z1. During annealing, no impurity ions are locally implanted between the first depth position Z1 and the second depth position Z2, other than the hydrogen ions and charged particles described above.

In the semiconductor substrate 10, the passage region 106 through which the charged particle has passed forms vacancy-based lattice defects such as monovacancies (V) and polyvacancies (VV) due to the passage of the charged particle. Atoms adjacent to the vacancies have dangling bonds. Lattice defects include interstitial atoms and dislocations, and may also include donors and acceptors in a broad sense. In this specification, vacancy-based lattice defects may be referred to as vacancy-type lattice defects, vacancy-type defects, or simply lattice defects. In addition, the injection of charged particles into the semiconductor substrate 10 may form many lattice defects, which may severely disrupt the crystallinity of the semiconductor substrate 10. In this specification, this disruption of crystallinity may be referred to as disorder.

The entire semiconductor substrate 10 contains oxygen. The oxygen is introduced intentionally or unintentionally during the manufacture of a semiconductor ingot. Inside the semiconductor substrate 10, hydrogen (H), vacancies (V), and oxygen (O) combine to form VOH defects. Furthermore, by subjecting the semiconductor substrate 10 to heat treatment, the hydrogen implanted at the first depth position Z1 diffuses, promoting the formation of VOH defects. If the charged particles implanted at the second depth position Z2 are hydrogen ions, hydrogen also diffuses from the second depth position Z2, further promoting the formation of VOH defects.

The VOH defect functions as a donor that supplies electrons. In this specification, the VOH defect may be simply referred to as a hydrogen donor. In this example, the hydrogen donor is formed in the charged particle passage region 106. The doping concentration of the hydrogen donor is lower than the chemical concentration of hydrogen. If the ratio of the doping concentration of the hydrogen donor to the chemical concentration of hydrogen is the activation rate, the activation rate may be a value between 0.1% and 30%. In this example, the activation rate is between 1% and 5%.

By forming hydrogen donors in the passing region 106 of the semiconductor substrate 10, the donor concentration in the passing region 106 can be made higher than the bulk donor concentration. Usually, a semiconductor substrate 10 having a predetermined bulk donor concentration must be prepared in accordance with the characteristics of the element to be formed in the semiconductor substrate 10, particularly the rated voltage or withstand voltage. In contrast, according to the semiconductor device 100 shown in FIG. 1, the donor concentration of the semiconductor substrate 10 can be adjusted by controlling the dose of charged particles and hydrogen ions. Therefore, the semiconductor device 100 can be manufactured using a semiconductor substrate 10 having a bulk donor concentration that does not correspond to the characteristics of the element. Although the variation in the bulk donor concentration during the manufacture of the semiconductor substrate 10 is relatively large, the dose of charged particles and hydrogen ions can be controlled with relatively high accuracy. Therefore, the concentration of lattice defects caused by the injection of charged particles can be controlled with high accuracy, and the concentration of hydrogen that binds to the lattice defects can also be controlled with high accuracy. Therefore, the donor concentration in the passing region 106 can be controlled with high accuracy.

In addition, it is preferable that the hydrogen implanted at the first depth position Z1 diffuses to a position farther toward the upper surface 21. This allows the length of the passing region 106 in the Z-axis direction to be increased, making it easier to adjust the doping concentration over a wide region of the semiconductor substrate 10.

When impurities other than the hydrogen ions and charged particles described above are implanted between the first depth position Z1 and the second depth position Z2, many lattice defects are formed near the implantation position. In the region where many lattice defects are formed, the diffusion of hydrogen ions is suppressed. Therefore, if a region with a high density of lattice defects exists between the first depth position Z1 and the second depth position Z2, the diffusion of hydrogen is suppressed.

In this example, after the first stage S1001 in which hydrogen injected into the first depth position Z1 is diffused into the passage region 106, other doping concentration peaks 111-2, 111-3, and 111-4 are formed in the second stage S1002. That is, in the second stage S1002, N-type dopants such as hydrogen ions are injected and annealed at one or more depth positions between the first depth position Z1 and the second depth position Z2. This forms the doping concentration peaks 111-2, 111-3, and 111-4. In this way, by forming the doping concentration peaks 111-2, 111-3, and 111-4 after diffusing the hydrogen injected into the first depth position Z1, it is possible to both diffuse hydrogen to a deeper position and provide multiple doping concentration peaks 111 in the buffer region 20.

2 shows the distributions of the lattice defect density D _V , hydrogen chemical concentration C _H , doping concentration D _d and impurity chemical concentration C _I in the depth direction at the position shown by the line A-A in FIG. 1. The impurity in this example is helium or hydrogen. The horizontal axis of FIG. 2 shows the depth position from the lower surface 23, and the vertical axis shows the hydrogen chemical concentration, donor concentration and impurity chemical concentration per unit volume on a logarithmic axis. Among the distributions in FIG. 2, the lattice defect density D _V is the distribution at the start of annealing in the first stage S1001 shown in FIG. 1. The concentrations other than the lattice defects show the distributions after annealing in the second stage S1002 shown in FIG. 1.

The hydrogen chemical concentration and impurity chemical concentration in FIG. 2 are measured, for example, by the SIMS method. The doping concentration in FIG. 2 is an electrically activated doping concentration measured, for example, by the CV method or the SR method.

In this example, the hydrogen chemical concentration C _H has a hydrogen chemical concentration peak 131-1 at the first depth position Z1. The hydrogen chemical concentration peak 131 shows a maximum value at the first depth position Z1. The hydrogen chemical concentration C _H also has a hydrogen chemical concentration peak 131 at a third depth position Z3. A plurality of third depth positions Z3 may be arranged. In the example of FIG. 2, third depth positions Z3-1, Z3-2, and Z3-3 are arranged. A hydrogen chemical concentration peak 131 is arranged at each of the third depth positions Z3. The hydrogen chemical concentration peaks 131-2 to 131-4 are peaks due to the hydrogen ions implanted in the second stage S1002 of FIG. 1.

The impurity chemical concentration C _I in this example has an impurity chemical concentration peak 141 at the second depth position Z2. The impurity chemical concentration peak 141 exhibits a maximum value at the second depth position Z2.

The doping concentration _Dd has a plurality of doping concentration peaks 111 and a doping concentration peak 121. In this example, the doping concentration peaks 111 are located at the first depth position Z1 and at the respective third depth positions Z3. The doping concentration _Dd may also have a doping concentration peak in the lower surface region 201. In this example, the lower surface region 201 has a P-type doping concentration peak. The lower surface region 201 may be implanted with a P-type dopant such as boron. In another example, the lower surface region 201 may have an N-type doping concentration peak. In this case, the lower surface region 201 may be implanted with an N-type dopant such as phosphorus.

In this example, the doping concentration peak 111 is a concentration peak of a hydrogen donor (VOH defect) formed by hydrogen bonding with a lattice defect caused by implantation of hydrogen ions at the first depth position Z1 and the third depth position Z3. Therefore, the doping concentration peak 111 shows a maximum value at the first depth position Z1 and each of the third depth positions Z3.

The doping concentration peak 121 is a concentration peak of hydrogen donors formed by combining lattice defects caused by the injection of charged particles at the second depth position Z2 with hydrogen diffused from the first depth position Z1. Therefore, the doping concentration peak 121 shows a maximum value at the second depth position Z2.

The position where the doping concentration peak 111-1 shows the maximum value does not have to strictly coincide with the first depth position Z1. For example, if the position where the doping concentration peak 111-1 shows the maximum value is included within the full width at half maximum range of the first hydrogen chemical concentration peak 131 based on the first depth position Z1, the doping concentration peak 111-1 may be substantially located at the first depth position Z1. Similarly, if the position where the doping concentration peak 121 shows the maximum value is included within the full width at half maximum range of the impurity chemical concentration peak 141 based on the second depth position Z2, the doping concentration peak 121 may be substantially located at the second depth position Z2. Similarly, if the position where the doping concentration peak 111 shows the maximum value is included within the full width at half maximum range of the hydrogen chemical concentration peak 131 based on the third depth position Z3, the doping concentration peak 111 may be substantially located at the third depth position Z3.

In addition, if the doping concentration peak 111-1 overlaps with the doping concentration peak of the lower surface region 201 and is difficult to distinguish, the doping concentration at the depth position Z1 of the apex of the hydrogen chemical concentration peak 131-1 may be taken as the doping concentration peak 111-1.

Each concentration peak has a lower foot where the concentration decreases from the apex towards the lower surface 23, and an upper foot where the concentration decreases from the apex towards the upper surface 21. In this example, hydrogen chemical concentration peak 131 has a lower foot 132 and an upper foot 133. Impurity chemical concentration peak 141 has a lower foot 142 and an upper foot 143. Doping concentration peak 111 has a lower foot 112 and an upper foot 113. Doping concentration peak 121 has a lower foot 122 and an upper foot 123.

Hydrogen ions are implanted from the lower surface 23 into the first depth position Z1 and the third depth position Z3, so that hydrogen is present in relatively large amounts between the first depth position Z1 and the lower surface 23, and between the third depth position Z3 and the lower surface 23. Similarly, impurities implanted as charged particles are present in large amounts between the second depth position Z1 and the lower surface 23. Therefore, at each concentration peak in each chemical concentration distribution, the concentration may decrease more steeply at the upper foot than at the lower foot. In addition, since the doping concentration depends on the hydrogen chemical concentration or the impurity chemical concentration, the concentration may also decrease more steeply at the upper foot than at the lower foot of each doping concentration peak.

At the start of the annealing in the first step S1001, a relatively large number of lattice defects are formed in the vicinity of the first depth position Z1 and the second depth position Z2 due to the implantation of hydrogen ions or charged particles. Therefore, the lattice defect concentration _DV has a first defect density peak 211 at the first depth position Z1 and a second defect density peak 212 at the second depth position Z2. In addition, in the passing region 106 (see FIG. 1) from the second depth position Z2 to the lower surface 23, lattice defects caused by the passage of the charged particles are formed at a substantially uniform density, except for the vicinity of the first depth position Z1 and the second depth position Z2. As shown by the dotted line in the distribution diagram of the lattice defect density _DV in FIG. 2, the lattice defect concentration _DV may increase gradually toward the peak 212 without exceeding the peak 212. Thus, even when the lattice defect concentration _DV increases toward the peak 212, the lattice defects caused by the passage of the charged particles may be formed at a substantially uniform density.

The hydrogen implanted at the first depth position Z1 diffuses toward the upper surface 21 by the annealing process. At the start of the annealing in the first step S1001, hydrogen ions are not implanted at the third depth position Z3. Therefore, there are no defect density peaks other than the first defect density peak 211 and the second defect density peak 212 between the first depth position Z1 and the second depth position Z2. Therefore, hydrogen is easily diffused from the first depth position Z1 to the second depth position Z2. In the region in which hydrogen of a certain concentration or more is diffused in the passing region 106, VOH defects (hydrogen donors) are formed, and a high concentration region 150 including hydrogen donors is formed. The high concentration region 150 is a region in which the donor concentration is higher than the bulk donor concentration _Db . The high concentration region 150 is disposed between the buffer region 20 and the upper surface 21 of the semiconductor substrate 10.

The high concentration region 150 may be a region with a substantially uniform doping concentration in the depth direction. A doping concentration that is substantially uniform in the depth direction may refer to, for example, a state in which a region in which the difference between the maximum and minimum values of the doping concentration is within 50% of the maximum doping concentration is continuous in the depth direction. The difference may be 30% or less of the maximum doping concentration of the region, or 10% or less.

Alternatively, the value of the doping concentration distribution may be within ±50%, ±30%, or ±10% of the average concentration of the doping concentration distribution in a predetermined range in the depth direction. The predetermined range W in the depth direction may be as follows, for example. That is, the length from the first depth position Z1 to the second depth position Z2 is _ZL , and the range may be a section of _0.5ZL between two points _0.25ZL away from the center _Z12c between Z1 and Z2 on the first depth position Z1 side and the second depth position Z2 side. Depending on the length of the high concentration region 150, the length of the predetermined range may be _0.75ZL , _0.3ZL , or _0.9ZL . The end position of the buffer region 20 on the upper surface 21 side may be the depth position where the substantially uniform doping concentration in the high concentration region 150 starts to increase monotonically toward the doping concentration peak 111-1.

In addition, at the start of annealing in the first stage S1001, it is preferable that there are no doping concentration peaks other than doping concentration peak 111-1 and doping concentration peak 121 between the first depth position Z1 and the second depth position Z2. It is also preferable that there are no chemical concentration peaks other than hydrogen chemical concentration peak 131-1 and impurity chemical concentration peak 141 between the first depth position Z1 and the second depth position Z2. This makes it easier for hydrogen to diffuse from the first depth position Z1 to the second depth position Z2.

By facilitating hydrogen diffusion, it becomes easier to form the high concentration region 150 long in the depth direction. The high concentration region 150 may be provided continuously from the position where it contacts the doping concentration peak 111-1 to the impurity chemical concentration peak 141. The high concentration region 150 may be provided continuously from the upper end of the buffer region 20 to the second depth position Z2.

The length of the high concentration region 150 in the depth direction may be 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more of the thickness of the semiconductor substrate 10 in the depth direction. The length of the high concentration region 150 may be the length L1 from the upper end of the buffer region 20 to the upper end of the high concentration region 150, or the length L2 from the position Z1 of the doping concentration peak 111-1 to the upper end of the high concentration region 150. The upper end of the high concentration region 150 may be the depth position Z2. The length of the high concentration region 150 in the depth direction may be 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 90 μm or more, or 100 μm or more. In this example, hydrogen is likely to diffuse up to the second depth position Z2, so the range in which the high concentration region 150 is formed is easily defined by the second depth position Z2.

The minimum value of the donor concentration of the high concentration region 150 is higher than the bulk donor concentration _Db of the semiconductor substrate 10. That is, the donor concentration (or doping concentration) of the high concentration region 150 is higher than the bulk donor concentration _Db throughout the entire high concentration region 150. The donor concentration of the high concentration region 150 is determined by the sum of the bulk donor concentration and the hydrogen donor concentration (VOH defect concentration). The hydrogen donor concentration can be precisely controlled by the dose of the charged particles at the second depth position Z2 and the dose of the hydrogen ions at the first depth position Z1. Therefore, by making the hydrogen donor concentration sufficiently higher than the bulk donor concentration, the variation in the donor concentration of the high concentration region 150 can be reduced even if the bulk donor concentration varies. The donor concentration of the high concentration region 150 may be twice or more, five times or more, or ten times or more, of the bulk donor concentration _Db .

3 shows the distributions of the lattice defect density D _V , the hydrogen chemical concentration C _H , the doping concentration D _d and the impurity chemical concentration C _I according to the comparative example. In the semiconductor device of the comparative example, hydrogen ions are implanted into the first depth position Z1 and each of the third depth positions Z3, and then the semiconductor substrate 10 is annealed to diffuse the hydrogen implanted into the first depth position Z1.

The lattice defect density _DV of this example has a defect density peak 213 at each of the third depth positions Z3 at the start of the annealing that diffuses the hydrogen ions. That is, one or more defect density peaks 213 are provided between the first depth position Z1 and the second depth position Z2. Therefore, the diffusion of hydrogen implanted at the first depth position Z1 is hindered by the defect density peaks 213. For example, hydrogen bonds with the lattice defects, or the presence of the lattice defects hinders the movement of hydrogen.

Therefore, in the example of FIG. 3, hydrogen does not sufficiently diffuse up to the second depth position Z2. In this case, the high concentration region 150 is not formed up to the second depth position Z2, and the low concentration region 181 with a low donor concentration remains. The donor concentration of the low concentration region 181 may be approximately the same as the bulk donor concentration _Db . In addition, when many lattice defects remain in the low concentration region 181, the carrier concentration of the low concentration region 181 may be lower than the bulk donor concentration _Db . Since almost no hydrogen donors are formed in the low concentration region 181, the donor concentration of the low concentration region 181 is largely influenced by the bulk donor concentration. Therefore, the donor concentration of the low concentration region 181 varies relatively widely. In addition, a valley-shaped portion is formed in the doping concentration distribution, which may affect the characteristics of the semiconductor device 100. In contrast, according to the semiconductor device 100 shown in FIG. 2, the high concentration region 150 can be formed widely, so that the variation in doping concentration can be suppressed and the characteristics of the semiconductor device 100 can be adjusted with high precision.

In the buffer region 20, it is also possible to make the hydrogen chemical concentration peak 131-4 closest to the upper surface 21 high-concentration. This makes it easier to diffuse hydrogen to a position close to the upper surface 21. However, if the hydrogen chemical concentration peak 131-4 close to the upper surface 21 is made high-concentration, the depletion layer may reach the high-concentration doping concentration peak 111-4 when the emitter-collector voltage is relatively high, and the avalanche resistance may decrease. According to the example shown in FIG. 2, the high-concentration doping concentration peak 111-1 is disposed near the lower surface 23 to suppress the decrease in the avalanche resistance, while the high-concentration region 150 can be formed up to the vicinity of the upper surface 21. The distance between the first depth position Z1 and the lower surface 23 may be 5 μm or less, or may be 3 μm or less.

4 is a diagram showing the distribution of hydrogen chemical concentration C _H and doping concentration D _d in the vicinity of the buffer region 20. In this example, the peak concentration of the doping concentration peak 111-1 is designated as A, the peak concentration of the doping concentration peak 111-2 is designated as B2, the peak concentration of the doping concentration peak 111-3 is designated as B3, and the peak concentration of the doping concentration peak 111-4 is designated as B4. In addition, the peak concentration of the hydrogen chemical concentration peak 131-1 is designated as H1-1, the peak concentration of the hydrogen chemical concentration peak 131-2 is designated as H1-2, the peak concentration of the hydrogen chemical concentration peak 131-3 is designated as H1-3, and the peak concentration of the hydrogen chemical concentration peak 131-4 is designated as H1-4.

The ratio A/B of the peak concentration A of the doping concentration peak 111-1 to the average peak concentration B (in this example, (B2+B3+B4)/3) of the other doping concentration peaks 111 is 200 or less. The average peak concentration B may be 10 ^{{log10(B2)+log10(B2)+log10(B2)}/3} . In the semiconductor device 100, hydrogen implanted at the first depth position Z1 is likely to diffuse toward the upper surface 21, so even if the peak concentration A is reduced, the high concentration region 150 can be formed over a long range. In addition, by reducing the peak concentration A, the occurrence of a back surface avalanche when the depletion layer from the upper surface 21 side reaches the doping concentration 111-1 can be suppressed. The ratio A/B may be 100 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less. However, if the peak concentration A of the doping concentration peak 111-1 is too low, hydrogen may not be sufficiently diffused. The ratio A/B may be 2 or more, 3 or more, 5 or more, or even 10 or more. The peak concentration A may be 1×10 ¹⁶ /cm ³ or less, 5×10 ¹⁵ /cm ³ or less, or 1×10 ¹⁵ /cm ³ or less.

The ratio H1-1/HA of the peak concentration H1-1 of hydrogen chemical concentration peak 131-1 to the average peak concentration HA of the other hydrogen chemical concentration peaks 131 (in this example, (H1-2+H1-3+H1-4)/3) may also be 200 or less. The ratio H1-1/HA may be 100 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less. The ratio H1-1/HA may be 2 or more, 3 or more, 5 or more, or 10 or more.

The dose (ions/cm ² ) of hydrogen ions at the first depth position Z1 is denoted by C, and the total dose of hydrogen ions at each of the third depth positions Z3 is denoted by D. The dose C is the dose corresponding to the doping concentration peak 111-1, and the dose D is the dose corresponding to the other doping concentration peaks 111. The dose corresponding to each doping concentration peak 111 may be a value obtained by integrating the hydrogen chemical concentration _CH within the full width at half maximum range of each doping concentration peak 111.

The ratio C/D of the dose amount C to the total dose amount D may be 6 or more and 100 or less. This makes it easier to suppress the occurrence of back surface avalanche while ensuring the length of the high concentration region 150. The ratio C/D may be 10 or more. The ratio C/D may be 30 or less.

Figure 5A is a flowchart showing an example of a method for manufacturing the semiconductor device 100. First, in the upper surface side structure formation step S500, a structure on the upper surface 21 side of the semiconductor substrate 10 is formed. The structure on the upper surface 21 side includes at least a portion of the gate trench, dummy trench, emitter region, base region, accumulation region, interlayer insulating film, emitter electrode, and gate wiring, which will be described later. All of these structures may be formed in the upper surface side structure formation step S500.

Next, in the grinding step S502, the lower surface 23 side of the semiconductor substrate 10 is ground to adjust the thickness of the semiconductor substrate 10. In the grinding step S502, the thickness of the semiconductor substrate 10 may be adjusted according to the withstand voltage that the semiconductor device 100 should have.

Next, in the lower surface region forming step S504, the lower surface region 201 is formed in the region in contact with the lower surface 23 of the semiconductor substrate 10. In the lower surface region forming step S504, the lower surface region 201 may be formed by injecting an N-type dopant or a P-type dopant from the lower surface 23 and locally annealing the vicinity of the lower surface 23 with a laser or the like.

Next, in the first implantation step S505, charged particles and hydrogen ions are implanted into the semiconductor substrate 10. The first implantation step S505 includes a charged particle implantation step S506 and a hydrogen implantation step S508. In the charged particle implantation step S506, charged particles are implanted from the lower surface 23 of the semiconductor substrate 10 to a second depth position Z2. The second depth position Z2 is closer to the upper surface 21 than the first depth position Z1. The charged particles may be hydrogen ions, helium ions, or electron beams. In the hydrogen implantation step S508, hydrogen ions are implanted from the lower surface 23 of the semiconductor substrate 10 to a first depth position Z1. In the hydrogen implantation step S508, hydrogen ions may be implanted at the first position Z1 so that the hydrogen chemical concentration distribution has a single peak in the region between the second depth position Z2 and the first depth position Z1. When hydrogen ions are implanted at the second depth position Z2, a peak of the hydrogen chemical concentration may exist at the second depth position Z2. Either the charged particle implantation step S506 or the hydrogen implantation step S508 may be performed first.

Next, in the first annealing step S510, the semiconductor substrate 10 is annealed. The first implantation step S505 and the first annealing step S510 correspond to the first step S1001 in FIG. 1. In the first annealing step S510, the semiconductor substrate 10 is placed in an annealing furnace, and the entire semiconductor substrate 10 is annealed. The first annealing step S510 forms a high concentration region 150 between the first depth position Z1 and the second depth position Z2. It is preferable that the first annealing step S510 is performed under conditions that allow the hydrogen injected into the first depth position Z1 to diffuse to the second depth position Z2. For example, the annealing temperature in the annealing step S510 is 350° C. or more and 400° C. or less. The annealing temperature may be 360° C. or more and 380° C. or less. The annealing time in the first annealing step S510 may be 30 minutes or more, 1 hour or more, or 3 hours or more. The annealing time may be 10 hours or less, or may be 7 hours or less.

Next, in the second implantation step S512, an N-type dopant such as hydrogen is implanted at the third depth position Z3. As described in FIG. 2 and the like, the third depth position Z3 may be located at one or more locations in the depth direction. The first depth position Z1 and each of the third depth positions Z3 may be located on the lower surface 23 side of the semiconductor substrate 10. The second depth position Z2 may be located on the upper surface 21 side of the semiconductor substrate 10.

Next, in the second annealing step S514, the semiconductor substrate 10 is annealed. The second implantation step S512 and the second annealing step S514 correspond to the second step S1002 in FIG. 1. In the second annealing step S514, the semiconductor substrate 10 may be placed in an annealing furnace to anneal the entire semiconductor substrate 10. The second annealing step S514 activates the N-type dopant implanted at the third depth position Z3 to form one or more doping concentration peaks 111. The annealing conditions in the second annealing step S514 are the same as those in the first annealing step S510. That is, the annealing temperature in the second annealing step S514 may be 350° C. or more and 400° C. or less. The annealing temperature may be 360° C. or more and 380° C. or less. The annealing time in the second annealing step S514 may be 30 minutes or more, 1 hour or more, or 3 hours or more. The annealing time may be 10 hours or less, or may be 7 hours or less.

The difference between the annealing temperature T2 in the second annealing step S514 and the annealing temperature T1 in the first annealing step S510 may be 10°C or less. The difference in the annealing temperature may be 5°C or less, or may be 0. The annealing temperatures T1 and T2 may be T1=T2, T2<T1, or T2>T1, under the condition that the difference in the annealing temperature satisfies the above. In this example, T1=T2. The difference in the annealing time between the second annealing step S514 and the first annealing step S510 may be 10% or less of the larger annealing time, 5% or less, or may be 0. By making the annealing conditions of the second annealing step S514 equivalent to those of the first annealing step S510, the disappearance of the hydrogen donors formed in the first annealing step S510 can be suppressed.

In the lower electrode formation step S520, a metal electrode is formed on the lower surface 23 of the semiconductor substrate 10. The metal electrode may be a collector electrode, which will be described later. In addition, between the second annealing step S514 and the lower electrode formation step S520, a lifetime killer formation step S516 and a third annealing step S518 may be included.

In the lifetime killer formation step S516, impurities such as helium are injected into the semiconductor substrate 10 to locally form lattice defects. The impurities may be injected into the upper surface 21 side or the lower surface 23 side of the semiconductor substrate 10. The impurities may be injected into a diode portion, which will be described later. The impurities may also be injected into a transistor portion, which will be described later. In the third annealing step S518, the semiconductor substrate 10 is annealed to adjust the density of the lattice defects. The annealing temperature T3 in the third annealing step S518 may be equal to or lower than the annealing temperature T1 in the first annealing step S510. Alternatively, the annealing temperature T3 in the third annealing step S518 may be equal to or lower than the annealing temperature T2 in the second annealing step S510.

Figure 5B is a flowchart showing another example of a method for manufacturing the semiconductor device 100. In this example, the order of the charged particle injection step S506 and the hydrogen injection step S508 is reversed compared to the example shown in Figure 5A. That is, in this example, the charged particle injection step S506 is performed after the hydrogen injection step S508. After the charged particle injection step S506, the first annealing step S510 is performed. The other steps may be the same as those in the example shown in Figure 5A. This example also allows the high concentration region 150 to be formed long in the depth direction.

Figure 6A is a flowchart showing another example of a method for manufacturing the semiconductor device 100. The manufacturing method of this example differs from the example shown in Figure 5A in the second injection step S512. The other steps may be similar to the example shown in Figure 5A.

In this example, in the second implantation step S512, hydrogen ions are implanted not only at the third depth position Z3, but also at the first depth position Z1. In other words, hydrogen ions are implanted at the first depth position Z1 in two steps, the first implantation step S505 and the second implantation step S512.

By implanting hydrogen ions at the third depth position Z3, a high density of lattice defects is formed near the third depth position Z3. The second annealing step S514 causes the hydrogen implanted at the third depth position Z3 to diffuse and bond with these lattice defects. However, since the dose of hydrogen implanted at the third depth position Z3 is relatively low, many lattice defects may remain. In contrast, by implanting hydrogen ions also at the first depth position Z1 in the second implantation step S512, the hydrogen implanted at the first depth position Z1 bonds with lattice defects near the third depth position Z3, thereby reducing the lattice defect density.

Figure 6B is a flow chart showing another example of a method for manufacturing the semiconductor device 100. In this example, the order of the charged particle injection step S506 and the hydrogen injection step S508 is reversed compared to the example shown in Figure 6A. That is, in this example, the charged particle injection step S506 is performed after the hydrogen injection step S508. After the charged particle injection step S506, the first annealing step S510 is performed. The other steps may be the same as in the example shown in Figure 6A. This example also allows the high concentration region 150 to be formed long in the depth direction.

7 is a diagram showing an example of the distribution of hydrogen chemical concentration _CH in the vicinity of the buffer region 20. The distribution of hydrogen chemical concentration _CH in FIG. 7 is the distribution after the second annealing step S514. The hydrogen chemical concentration due to the hydrogen injected in the first implantation step S505 is defined as _CH0 . This hydrogen is diffused toward the upper surface 21 by the first annealing step S510. The peak value of the hydrogen chemical concentration _CH0 after the first annealing step S510 is defined as H1-0.

Next, in a second implantation step S512, hydrogen ions are implanted into the first depth position Z1 and each of the third depth positions Z3. An N-type dopant such as phosphorus may be implanted into the third depth position Z3 instead of hydrogen ions. In the second annealing step S514, the hydrogen additionally implanted into the first depth position Z1 diffuses to the vicinity of each of the third depth positions Z3. This reduces the lattice defect density in the vicinity of each of the third depth positions Z3. The peak value of the hydrogen chemical concentration C _H after the second annealing step S514 is designated as H1-1.

An N-type dopant such as phosphorus may be additionally implanted into the buffer region 20. In FIG. 7, an example distribution of the phosphorus chemical concentration C _P is shown by a dashed line. The phosphorus chemical concentration C _P may have a chemical concentration peak 171 between the lower surface 23 and the depth position Z1. The concentration of the peak 171 may be greater or less than the peak value H1-1. The concentration of the peak 171 may be greater or less than the peak value H1-0.

Peak value H1-0 may be greater than any of the peak values of hydrogen chemical concentration peaks 131-2, 131-3, and 131-4. By increasing the concentration of hydrogen ions implanted in the first implantation step S505, hydrogen can be diffused to a deeper position. The dose of hydrogen ions implanted at the first depth position Z1 in the first implantation step S505 may be greater than the total dose of hydrogen ions implanted at each of the second depth positions Z3 in the second implantation step S512.

The difference between the peak value H1-1 and the peak value H1-0 may be smaller than the peak value H1-0. That is, the second dose of hydrogen ions implanted at the first depth position Z1 in the second implantation stage S512 may be lower than the first dose of hydrogen ions implanted at the first depth position Z1 in the first implantation stage S505. In the second implantation stage S512, since it is sufficient to terminate the lattice defects in the vicinity of the third depth position Z3, the dose of hydrogen ions may be small. The second dose may be half or less of the first dose. The first dose may be 1×10 ¹⁴ ions/cm ³ or more. The first dose may be 2×10 ¹⁴ ions/cm ³ or more, or may be 5×10 ¹⁴ ions/cm ³ or more. The second dose may be 5×10 ¹³ ions/cm ³ or more, or may be 1×10 ¹⁴ ions/cm ³ or more.

8 is a diagram showing a change in doping concentration _Dd in the vicinity of the buffer region 20 when the dose of hydrogen ions at the first depth position Z1 is changed. In this example, in the second implantation stage 512, no hydrogen ions are implanted at the first depth position Z1. Also, the dose of hydrogen ions at each of the third depth positions Z3 is not changed.

The doping concentration D _d1 is the doping concentration when the dose of hydrogen ions at the first depth position Z1 is 1×10 ¹⁴ /cm ^2. The doping concentration D _d2 is the doping concentration when the dose of hydrogen ions at the first depth position Z1 is 3×10 ¹³ /cm ^2. The doping concentration D _d3 is the doping concentration when the dose of hydrogen ions at the first depth position Z1 is 1×10 ¹³ /cm ^2. The dose of hydrogen ions at the third depth position Z3 closest to the first depth position Z1 is 1×10 ¹³ /cm ² .

Regardless of the dose, the doping concentration distribution on the upper surface 21 side of the doping concentration peak 111-2 does not change much. In contrast, the doping concentration between the doping concentration peak 111-1 and the doping concentration peak 111-2 changes significantly depending on the dose at the first depth position Z1. Note that even when the dose at the first depth position Z1 is increased beyond 1×10 ¹⁴ /cm ² , the doping concentration between the doping concentration peak 111-1 and the doping concentration peak 111-2 hardly changes.

For this reason, it is considered that when the dose amount for the first depth position Z1 is small, the lattice defects between the doping concentration peak 111-1 and the doping concentration peak 111-2 are not sufficiently bonded with hydrogen. The dose amount of hydrogen ions for the first depth position Z1 may be 3×10 ¹³ /cm ² or more, or may be 1×10 ¹⁴ /cm ² or more. The dose amount of hydrogen ions for the first depth position Z1 may be three times or more, or may be ten times or more, of the dose amount of hydrogen ions for the third depth position Z3 closest to the first depth position Z1. In addition, the doping concentration of the doping concentration peak 111-1 may be three times or more, or may be ten times or more, of the doping concentration of the doping concentration peak 111-2.

Figure 9A is a diagram explaining the relationship between the hydrogen chemical concentration peak 131-1 and the doping concentration peak 111-1. In this example, the slope 114 of the lower foot 112 of the doping concentration peak 111-1 is normalized using the slope 134 of the lower foot 132 of the hydrogen chemical concentration peak 131-1. As an example of normalization, the slope 114 is divided by the slope 134.

The slope of the lower tail may be the slope between the position where the concentration shows a maximum value and the position where the concentration is a predetermined ratio to the maximum value. The predetermined ratio may be 80%, 50%, 10%, 1%, or another ratio may be used. Also, for the hydrogen chemical concentration peak 131-1 and the doping concentration peak 111-1, the slope of the concentration distribution between the first depth position Z1 and the lower surface 23 of the semiconductor substrate 10 may be used.

9A, the slope 134 of the hydrogen chemical concentration peak 131-1 is given by (H1-aH1)/(Z1-Z4), and the slope 114 of the doping concentration peak 111-1 is given by (D1-aD1)/(Z1-Z5). H1 is the hydrogen chemical concentration at the first depth position Z1, D1 is the doping concentration at the first depth position Z1, a is a predetermined ratio, Z4 is the depth at which the hydrogen concentration becomes aH1 at the lower foot 132 of the hydrogen chemical concentration peak 131-1, and Z5 is the depth at which the doping concentration becomes aD1 at the lower foot 112 of the doping concentration peak 111-1. For example, when the slope 114 is normalized by the slope 134, it becomes (D1-aD1)(Z1-Z4)/{(H1-aH1)(Z1-Z5)}. The slope obtained by normalizing the slope 114 with the slope 134 is defined as α.

Figure 9B is a diagram illustrating the relationship between the impurity chemical concentration peak 141 and the doping concentration peak 121. In this example, hydrogen ions are implanted as charged particles at the second depth position Z2. In this example, the slope 144 of the lower foot 142 of the impurity chemical concentration peak 141 is used to normalize the slope 124 of the lower foot of the doping concentration peak 121.

9B, the slope 144 of the impurity chemical concentration peak 141 is given by (H2-aH2)/(Z2-Z6), and the slope 124 of the doping concentration peak 121 is given by (D2-aD2)/(Z2-Z7). H2 is the hydrogen chemical concentration at the second depth position Z2, D2 is the doping concentration at the second depth position Z2, a is a predetermined ratio, Z6 is the depth at which the hydrogen chemical concentration is aH2 at the lower foot 142 of the impurity chemical concentration peak 141, and Z7 is the depth at which the doping concentration is aD2 at the lower foot 122 of the doping concentration peak 121. The ratio a used to normalize the slope of the doping concentration peak 121 may be the same as or different from the ratio a used to normalize the slope of the doping concentration peak 111-1. For example, when the slope 124 is normalized by the slope 144, it becomes (D2-aD2)(Z2-Z6)/{(Z2-Z7)(H2-aH2)}. The slope obtained by normalizing the slope 124 by the slope 144 is defined as β.

The normalized slope β of the lower foot 122 of the doping concentration peak 121 is smaller than the normalized slope α of the lower foot 112 of the doping concentration peak 111-1. In other words, the doping concentration peak 121 is a gentler peak relative to the hydrogen chemical concentration peak than the doping concentration peak 111-1. By injecting hydrogen ions so as to form such a doping concentration peak 121, a high concentration region 150 having a flat concentration distribution can be formed. In addition, by making the doping concentration peak 121 have a gentle shape, the change in doping concentration at the tip of the high concentration region 150 can be made gentle. The normalized slope β of the lower foot 122 of the doping concentration peak 121 may be 1 time or less, 0.1 times or less, or 0.01 times or less of the normalized slope α of the lower foot of the doping concentration peak 111-1.

In addition, the slope 144 of the lower foot 142 of the impurity chemical concentration peak 141 may be smaller than the slope 145 of the upper foot 143. The chemical concentration distribution of hydrogen injected into a deep position from the lower surface 23 may have a gentle slope toward the lower surface 23, so by comparing the slope 144 of the lower foot 142 with the slope 145 of the upper foot 143, it may be possible to determine whether the hydrogen injected into the second depth position Z2 was injected from the lower surface 23 side. The slope 145 is given by (H2-aH2)/(Z8-Z2). The slope 125 is given by (D2-aD2)/(Z9-Z2). Z8 is the depth at which the hydrogen chemical concentration becomes aH2 at the upper foot 143 of the impurity chemical concentration peak 141, and Z9 is the depth at which the doping concentration becomes aD2 at the upper foot 123 of the doping concentration peak 121. In FIG. 9B, the slope 124 of the lower foot 122 of the doping concentration peak 121 is greater than the slope 125 of the upper foot 123, but similar to the impurity chemical concentration peak 141, the slope 124 of the lower foot 122 of the doping concentration peak 121 may be smaller than the slope 125 of the upper foot 123.

Figure 9C is a diagram explaining the slope of the lower skirt 142. The slope of the lower skirt 142 may be considered as follows. As shown in Figure 9C, the width (10% full width) between two positions P10 and P11 at which the concentration of the impurity chemical concentration peak 141 is 10% (0.1 x H2) of the peak concentration H2 is defined as FW10%M. The two positions P10 and P11 are the two positions closest to the second depth position Z2 among the points at which the hydrogen chemical concentration is 0.1 x H2, sandwiching the second depth position Z2. The position on the hydrogen chemical concentration peak 131-1 side of the two positions P10 and P11 is defined as Z10. The slope of the doping concentration at position Z10 is almost flat. The slope of the hydrogen chemical concentration at position Z10 is more than 100 times the slope of the doping concentration at position Z10. For example, the gradient of the hydrogen chemical concentration at position Z10 may be 100 times or more, or even 1000 times or more, than the gradient of the doping concentration at position Z10.

FIG. 10A is a diagram for explaining another definition of the normalization of the gradient of the lower skirt 112. In the normalization of the gradient of the lower skirt 112, for example, the following index γ is introduced. In the example of FIG. 9A, the position Z4 and the position Z5 are different, but in this example, the position Z4 and the position Z5 are the same position (Z4=Z5). Here, the position Z4 is a predetermined position. The position Z4 may be a position where the hydrogen chemical concentration C _H and the doping concentration D _d are the lower skirts 132, 112 on the lower surface 23 side from the first depth position Z1. The hydrogen chemical concentration at the position Z4 is a×H1, and the doping concentration is b×D1. a is the ratio of the hydrogen chemical concentration at the position Z4 to the concentration H1 of the hydrogen chemical concentration peak 131-1 at the first depth position Z1. b is the ratio of the doping concentration at the position Z3 to the concentration D1 of the doping concentration peak 111-1 at the first depth position Z1. Here, we introduce the ratio of the slopes of the hydrogen chemical concentration and the doping concentration in the section Z4 to Z1, and the slope ratio γ obtained by normalizing the slope ratio. The ratio of the slopes of the hydrogen chemical concentration in the section Z4 to Z1 is defined as (H1/aH1)/(Z1-Z4). Similarly, the ratio of the slopes of the donor concentrations in the section Z4 to Z1 is defined as (D1/bD1)/(Z1-Z4). Then, the slope ratio γ obtained by normalizing the ratio of the slopes of the doping concentrations by the ratio of the slopes of the hydrogen chemical concentrations in the section Z4 to Z1 is defined as {(D1/bD1)/(Z1-Z4)}/{(H1/aH1)/(Z1-Z4)}. The normalized slope ratio γ becomes the simple ratio a/b by calculating the above formula.

Figure 10B is a diagram explaining another definition of the normalization of the slope of the lower skirt 122. In the normalization of the slope of the lower skirt 122, for example, an index ε similar to the index γ is introduced. In the example of Figure 9B, the positions Z6 and Z7 were different, but in this example, the positions Z6 and Z7 are the same position (Z6 = Z7). Here, the position Z6 is a predetermined position. The position Z6 may be a position where the hydrogen chemical concentration and the doping concentration are the lower skirts 142, 122 on the lower surface 23 side from the second depth position Z2. The hydrogen chemical concentration at the position Z6 is c x H2, and the doping concentration is d x D2. c is the ratio of the hydrogen chemical concentration at the position Z6 to the hydrogen chemical concentration H2 at the second depth position Z2. d is the ratio of the doping concentration at the position Z6 to the concentration D2 of the doping concentration peak 121 at the second depth position Z2. Here, we introduce the ratio of the slopes of the hydrogen chemical concentration and the doping concentration in the section Z6 to Z2, and the slope ratio ε obtained by normalizing the slope ratio. The ratio of the slopes of the hydrogen chemical concentration in the section Z6 to Z2 is defined as (H2/cH2)/(Z2-Z6). Similarly, the ratio of the slopes of the doping concentrations in the section Z6 to Z2 is defined as (D2/dD2)/(Z2-Z6). Then, the slope ratio γ obtained by normalizing the ratio of the slopes of the doping concentrations by the ratio of the slopes of the hydrogen chemical concentrations in the section Z6 to Z2 is defined as {(D2/dD2)/(Z2-Z6)}/{(H2/cH2)/(Z2-Z6)}. The normalized slope ratio γ becomes a simple ratio (c/d) by calculating the above formula.

For the hydrogen chemical concentration peak 131-1 and the doping concentration peak 111-1, the hydrogen chemical concentration distribution and the doping concentration distribution often have similar shapes. Here, being similar means that, for example, when the horizontal axis is depth and the vertical axis is common logarithm of concentration, the doping concentration distribution shows a distribution that reflects the hydrogen chemical concentration distribution. That is, by ion-implanting hydrogen ions in a predetermined section Z4 to Z1 and then performing annealing, the doping concentration distribution becomes a distribution that reflects the hydrogen chemical concentration distribution. As an example, if H1 of the hydrogen chemical concentration peak 131-1 is 1×10 ¹⁷ atoms/cm ³ and the hydrogen chemical concentration aH1 at the position Z4 is 2×10 ¹⁶ atoms/cm ³ , then a is 0.2. On the other hand, if D1 of doping concentration peak 111-1 is 1×10 ¹⁶ /cm ³ and the doping concentration bD1 at position Z4 is 2×10 ¹⁵ /cm ³ , then b is 0.2. Therefore, the normalized slope ratio γ is a/b, which is 1. That is, at the first depth position Z1 close to the lower surface 23, the slope ratio a of the hydrogen chemical concentration distribution and the slope ratio b of the doping concentration distribution are approximately the same value, and can be said to be similar in shape.

On the other hand, for the impurity chemical concentration peak 141 and the doping concentration peak 121, the hydrogen chemical concentration distribution and the doping concentration distribution do not have to be similar. That is, in a predetermined section Z6 to Z2, the doping concentration distribution does not have to reflect the hydrogen chemical concentration distribution. As an example, if the hydrogen chemical concentration H2 of the impurity chemical concentration peak 141 is 1×10 ¹⁶ atoms/cm ³ and the hydrogen chemical concentration cH2 at the position Z6 is 1×10 ^{15 atoms} /cm ³ , c is 0.1. On the other hand, if the concentration D2 of the doping concentration peak 121 is 3×10 ¹⁴ /cm ³ and the doping concentration dD2 at the position Z6 is 1.5×10 14 /cm ³ , d is 0.5. Therefore, the normalized slope ratio ε is c/d, which is 0.2. That is, at the second depth position Z2 that is sufficiently deep from the lower surface 23, the ratio c of the slope of the hydrogen chemical concentration distribution is 0.2 times smaller than the ratio d of the slope of the doping concentration distribution, and it can be said that the shapes are far from similar.

When comparing the normalized slope ratios γ and ε, γ will be close to 1 when the peak position of the hydrogen chemical concentration distribution is close to the lower surface 23, and ε may be a value sufficiently higher than 1 when the peak position of the hydrogen chemical concentration distribution is sufficiently deep from the lower surface 23. In other words, the normalized slope ratio ε may be larger than the normalized slope ratio γ. Furthermore, the slope ratio ε may be 1.1 or more, 1.5 or more, or 2 or more. Alternatively, it may be 10 or more, or 100 or more.

Note that the actual positions of the hydrogen chemical concentration peak 131-1 and the impurity chemical concentration peak 141 may differ from the actual positions of the doping concentration peak 111-1 and the doping concentration peak 121. In this way, when the position of the chemical concentration peak does not match the position of the doping concentration, the position of the chemical concentration peak may be set to the first depth position Z1 or the second depth position Z2, and the concentration at the first depth position Z1 or the second depth position Z2 may be set to the peak position of the doping concentration for convenience. This makes it possible to perform calculations using the above definition.

Figures 11 to 19 are diagrams illustrating an example of a method for determining the preferred range of the bulk donor concentration and the donor concentration of the high concentration region 150. In this example, the bulk donor concentration and the donor concentration are set so that the final donor concentration (doping concentration) in the high concentration region 150 is a relatively stable concentration even if the bulk donor concentration varies.

In this example, the specification value of the bulk donor concentration is N _B0 , and the actual bulk donor concentration is N _Bre . The specification value of the bulk donor concentration is a specification value specified by the manufacturer of the semiconductor wafer. If there is a range of specification values, the median value of the specification values may be used. The bulk donor concentration is given by N=1/qμρ, where ρ is the resistivity determined by the concentration of a bulk donor such as phosphorus. q is the elementary charge, and μ is the mobility of electrons in the semiconductor substrate 10.

The concentration of hydrogen donors (VOH defects) is defined as N 1 _H. The variation in the hydrogen donor concentration N 1 _H is negligibly small compared to the variation in the bulk donor concentration. In this example, the variation in the hydrogen donor concentration N 1 _H is set to 0.

The target value of the final donor concentration is set to N _F0 . The final donor concentration actually obtained is set to N _Fre . The above concentrations are all concentrations per unit volume (/cm ³ ).

The final target value N _F0 of the donor concentration is obtained by adding the hydrogen donor concentration N _H to the specified value N _B0 of the bulk donor concentration, and is given by the following formula:
N _F0 = N _H + N _B0 ...Formula (1)
On the other hand, the actual donor concentration _{N_Fre} is obtained by adding the hydrogen donor concentration _{N_H} to the actual bulk donor concentration _{N_Bre} , and is given by the following equation:
N _Fre = _NH +N _Bre ...Formula (2)

The parameter β is defined by the following equation.
β=N _Bre /N _B0 ...Formula (3)
The parameter β is the ratio between the actual bulk donor concentration N _Bre and the specification value N _B0 , and the greater the deviation from 1, the greater the deviation of the actual bulk donor concentration N _Bre from the specification value N _B0 .

The parameter γ is defined as follows:
γ=N _Fre /N _F0 ...Formula (4)
The parameter γ is the ratio between the actual donor concentration N _Fre and the target value N _F0 , and the farther it is from 1, the more the actual donor concentration N _Fre deviates from the target value N _F0 . In other words, if γ is sufficiently close to 1, even if the actual bulk donor concentration N _Bre deviates from the specification value N _B0 by β times, the actual donor concentration N _Fre will almost match the target value N _F0 with almost no dependence on β.

Here, the specific resistance variation of silicon wafers manufactured by the FZ method, in which the variation in bulk donor concentration is relatively small, is generally as follows:
Neutron irradiated FZ wafers: ±8% (ratio: 0.92 to 1.08)
Gas-doped FZ wafer: ±12% (ratio: 0.88 to 1.12)
Therefore, if γ is 0.85 or more and 1.15 or less, the variation in the final donor concentration N _Fre becomes approximately the same as the bulk donor concentration of the silicon wafer obtained by the FZ method described above. In this specification, the allowable value of γ is 0.85 or more and 1.15 or less.

The actual donor concentration N _Fre is affected by the variation (β) of the actual bulk donor concentration N _Bre . On the other hand, the variation of the hydrogen donor concentration N _H can be considered to be almost zero compared to the variation of the bulk donor concentration N _Bre . Therefore, by making the specification value N _B0 of the bulk donor concentration smaller than the target value N _F0 of the donor concentration, it is possible to reduce the proportion of components that vary in the donor concentration N _Fre .

The parameter ε′ is defined by the following equation.
N _B0 = ε ' × N _F0 ... formula (5)
Here, 0<ε′<1. The parameter ε′ is a parameter meaning that the specification value _{N_B0} of the bulk donor concentration is set smaller by ε′ than the target value _{N_F0} of the donor concentration.
It is considered how small a value of ε′ should be from 1, but not zero, so that γ is independent of β and sufficiently approaches 1.

The parameter ε is defined by the following equation.
ε=1/ε'...Formula (6)
From equations (5) and (6), the following equation is obtained:
N _B0 = N _F0 / ε Equation (7)
By substituting equation (7) into equation (1), the following equation is obtained.
N _F0 = N _H + N _F0 / ε That is, N _H = (1 - 1/ε) N _F0 ... formula (8)
By substituting equations (8) and (3) into equation (2), the following equation is obtained.
N _Fre = (1-1/ε)N _F0 +βN _B0 ...Formula (9)
By substituting equation (7) into equation (9), the following equation is obtained.
N _Fre = (1-1/ε) N _F0 + (β/ε) N _F0
=(1-1/ε+β/ε)N _F0 ...Formula (10)
By substituting equation (10) into equation (4), the following equation is obtained.
γ=1−1/ε+β/ε
=1+(β-1)/ε...Formula (11)
From equations (6) and (11), the following equation is obtained:
γ=1+ε'(β-1) ...Formula (12)

11 is a graph showing the relationship between ε' and γ shown in formula (12) for each β. As described above, γ indicates the ratio of the actual donor concentration N _Fre to the target value N _F0 , and β indicates the ratio of the actual bulk donor concentration N _Bre to the specification value N _B0 . The allowable value of γ is 0.85 or more and 1.15 or less.

For example, the specification value N _B0 of the bulk donor concentration is set to 0.5 times or less the target value N _F0 of the donor concentration, that is, ε' is set to 0.5 or less. In this case, even if β is 1.3, γ is set to 1.15 or less, which is within the allowable range. In other words, even if the actual bulk donor concentration N _Bre is 30% higher than the specification value N _B0 , the actual donor concentration N _Fre is set to 1.15 times or less the target value N _F0 . Also, even if β is 0.7, γ is within the allowable range if ε' is 0.5 or less. When ε' approaches 0, γ converges to 1. For example, when β=2, γ is within the allowable range if ε' is approximately 0.2 or less.

In order to set γ within the above-mentioned allowable range, the following ranges A to D, for example, are considered as preferable ranges of ε'.
(Range A)
ε' is 0.001 or more and 0.5 or less. When ε' is 0.5, γ is within the allowable range if β is within the range of 0.7 to 1.3. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.001, the target value N _F0 of the donor concentration is 1×10 ¹¹ /cm ³ , which corresponds to approximately 46000 Ωcm.

(Range B)
ε' is 0.01 or more and 0.333 or less. When ε' is 0.333, γ is within the allowable range if β is within the range of 0.5 to 1.5. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.01, the target value N _F0 of the donor concentration is 1×10 ¹² /cm ³ , which corresponds to approximately 4600 Ωcm.

(Range C)
ε' is 0.03 or more and 0.25 or less. When ε' is 0.25, γ is within the allowable range if β is within the range of approximately 0.4 to 1.6. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.03, the target value N _F0 of the donor concentration is 3×10 ¹² /cm ³ , which corresponds to approximately 1500 Ωcm.

(Range D)
ε' is 0.1 or more and 0.2 or less. When ε' is 0.2, γ is within the allowable range if β is within the range of approximately 0.2 to 1.8. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.1, the target value N _F0 of the donor concentration is 1×10 ¹³ /cm ³ , which corresponds to approximately 460 Ωcm.

In addition, since the smaller the variation in resistivity, the more practical it is, the more preferable that ε' is 0.1 or less, and more preferably 0.02 or less. In this case, for example, the following ranges E to H are considered.
(Range E)
ε' is 0.001 or more and 0.1 or less. When ε' is 0.1, if β is within the range of approximately 0.05 (not shown) to 3.0, γ is sufficiently within the allowable range. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.1, the target value N _F0 of the donor concentration is 1×10 ¹³ /cm ³ , which corresponds to approximately 460 Ωcm.

(Range F)
ε' is 0.002 or more and 0.05 or less. When ε' is 0.05, if β is within the range of approximately 0.01 (not shown) to 5.0, γ is sufficiently within the allowable range. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.05, the target value N _F0 of the donor concentration is 5×10 ¹² /cm ³ , which corresponds to approximately 920 Ωcm.

(Range G)
ε' is 0.005 or more and 0.02 or less. When ε' is 0.02, if β is within the range of approximately 0.01 (not shown) to 10.0, γ is sufficiently within the allowable range. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.02, the target value N _F0 of the donor concentration is 2×10 ¹² /cm ³ , which corresponds to approximately 2300 Ωcm.

(Range H)
When ε' has a range of 0.01±0.002 (20%). When ε' is 0.01, if β is within the range of approximately 0.01 (not shown) to 20.0 (not shown), γ is sufficiently within the allowable range. For example, when the specification value N _B0 of the bulk donor concentration is 1×10 ¹⁴ /cm ³ and ε' is 0.01, the target value N _F0 of the donor concentration is 1×10 ¹² /cm ³ , which corresponds to approximately 4600 Ωcm.

As described above, the actual donor concentration N _Fre corresponds to the donor concentration of the high concentration region 150. The breakdown voltage of the semiconductor device 100 is determined substantially by the donor concentration of the high concentration region 150 which occupies a large area in the semiconductor substrate 10. Therefore, a preferable range of the donor concentration N _Fre of the high concentration region 150 is determined by the rated voltage of the semiconductor device 100. The range of the bulk donor concentration N _Bre in which the donor concentration N _Fre can be stabilized is determined according to the donor concentration N _Fre .

Fig. 12 is a diagram showing an example of a preferred range of the bulk donor concentration N _Bre . In this example, the donor concentration N _Fre (/cm ³ ) at the center Zc in the depth direction of the semiconductor substrate 10 is (9.20245×10 ¹⁵ )/x or more and (9.20245×10 ¹⁶ )/x, where x is the rated voltage (V). The donor concentration N _Fre (/cm ³ ) was determined with reference to the doping concentration of the drift region in a general semiconductor substrate formed by the FZ method, but it may also be determined with reference to the doping concentration of the drift region of a semiconductor substrate formed by the MCZ method. In Fig. 12 , the upper limit 311 and the lower limit 312 of the preferred range of the donor concentration N _Fre (/cm ³ ) are indicated by dashed lines.

In Fig. 12, the upper limit 313 and the lower limit 314 of the preferred range of the bulk donor concentration N _Bre in the above-mentioned range A (ε' is 0.001 or more and 0.5 or less) are shown by solid lines. The upper limit 313 of the bulk donor concentration N _Bre is a value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.5). The lower limit 314 of the bulk donor concentration N _Bre is a value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.001). The upper limit 313 and the lower limit 314 of the bulk donor concentration N _Bre are as follows. Note that the unit of the upper limit 313 and the lower limit 314 in each example is (/cm ³ ). As described above, x is the rated voltage (V).
・Lower limit 314: (9.20245×10 ¹² )/x
・Upper limit 313: (4.60123×10 ¹⁶ )/x

Fig. 13 is a diagram showing an example of a preferred range of the bulk donor concentration N _Bre when ε' is in the range B (0.01 or more and 0.333 or less). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.333). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.01). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows:
・Lower limit 314: (9.20245×10 ¹³ )/x
・Upper limit 313: (3.06442×10 ¹⁶ )/x

Fig. 14 is a diagram showing an example of a preferred range of the bulk donor concentration N _Bre when ε' is in the range C (0.03 or more and 0.25 or less). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.25). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.03). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows.
・Lower limit 314: (2.76074×10 ¹⁴ )/x
・Upper limit 313: (2.30061×10 ¹⁶ )/x

Fig. 15 is a diagram showing an example of a preferred range of the bulk donor concentration N _Bre when ε' is in the range D (0.1 or more and 0.2 or less). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.2). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.1). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows:
・Lower limit 314: (9.20245×10 ¹⁴ )/x
・Upper limit 313: (1.84049×10 ¹⁶ )/x

Fig. 16 is a diagram showing an example of a preferred range of the bulk donor concentration N _Bre when ε' is in the range E (0.001 or more and 0.1 or less). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.1). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.001). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows:
・Lower limit 314: (9.20245×10 ¹² )/x
・Upper limit 313: (9.20245×10 ¹⁵ )/x

Fig. 17 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε' is in the range F (0.002 or more and 0.05 or less). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.05). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.002). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows.
・Lower limit 314: (1.84049×10 ¹³ )/x
・Upper limit 313: (4.60123×10 ¹⁵ )/x

Fig. 18 is a diagram showing an example of a preferable range of the bulk donor concentration N _Bre when ε' is in the range G (0.005 or more and 0.02 or less). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.02). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.005). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows.
・Lower limit 314: (4.60123×10 ¹³ )/x
・Upper limit 313: (1.84049×10 ¹⁵ )/x

Fig. 19 is a diagram showing an example of a preferred range of the bulk donor concentration N _Bre when ε' is in the range H (0.01±0.002). The upper limit 311 and lower limit 312 of the donor concentration N _Fre (/cm ³ ) are the same as those in the example of Fig. 12. The upper limit 313 of the bulk donor concentration N _Bre is the value obtained by multiplying the upper limit 311 of the donor concentration N _Fre (/cm ³ ) by the upper limit value of ε' (0.01). The lower limit 314 of the bulk donor concentration N _Bre is the value obtained by multiplying the lower limit 312 of the donor concentration N _Fre (/cm ³ ) by the lower limit value of ε' (0.01). The upper limit 313 and lower limit 314 of the bulk donor concentration N _Bre are as follows:
・Lower limit 314: (9.20245×10 ¹³ )/x
・Upper limit 313: (9.20245×10 ¹⁴ )/x
In addition, the upper limit 313 and the lower limit 314 of each range may have a width of ±20%.

12 to 19, by setting the bulk donor concentration N _Bre to a concentration between the upper limit 313 and the lower limit 314 in each example, γ, which indicates the variation in the final donor concentration N _Fre , can be suppressed within an allowable range. Note that the curve of the lower limit 314 may be smaller than the intrinsic carrier concentration. Here, the intrinsic carrier concentration is 1.45×10 ¹⁰ /cm ³ at room temperature (e.g., 300 K). If the value of the curve of the lower limit 314 is smaller than the intrinsic carrier concentration, the lower limit 314 may be replaced with the intrinsic carrier concentration.

Figure 20 is an example of a top view of the semiconductor device 100. In Figure 20, the positions of each component projected onto the top surface of the semiconductor substrate 10 are shown. In Figure 20, only some of the components of the semiconductor device 100 are shown, and some components are omitted.

The semiconductor device 100 includes the semiconductor substrate 10 described in FIG. 1 to FIG. 19. The semiconductor substrate 10 has edges 102 when viewed from above. When simply referred to as a top view in this specification, it means that the semiconductor substrate 10 is viewed from the top side. In this example, the semiconductor substrate 10 has two sets of edges 102 that face each other when viewed from above. In FIG. 20, the X-axis and Y-axis are parallel to one of the edges 102. The Z-axis is perpendicular to the top surface of the semiconductor substrate 10.

An active portion 160 is provided on the semiconductor substrate 10. The active portion 160 is a region through which a main current flows in the depth direction between the upper and lower surfaces of the semiconductor substrate 10 when the semiconductor device 100 is in operation. An emitter electrode is provided above the active portion 160, but is omitted in FIG. 20.

The active section 160 is provided with at least one of a transistor section 70 including a transistor element such as an IGBT, and a diode section 80 including a diode element such as a free wheel diode (FWD). In the example of FIG. 20, the transistor section 70 and the diode section 80 are alternately arranged along a predetermined arrangement direction (the X-axis direction in this example) on the upper surface of the semiconductor substrate 10. In other examples, the active section 160 may be provided with only one of the transistor section 70 and the diode section 80.

20, the region in which the transistor section 70 is arranged is marked with the symbol "I", and the region in which the diode section 80 is arranged is marked with the symbol "F". In this specification, the direction perpendicular to the arrangement direction in a top view may be referred to as the extension direction (Y-axis direction in FIG. 20). The transistor section 70 and the diode section 80 may each have a longitudinal direction in the extension direction. In other words, the length of the transistor section 70 in the Y-axis direction is greater than its width in the X-axis direction. Similarly, the length of the diode section 80 in the Y-axis direction is greater than its width in the X-axis direction. The extension direction of the transistor section 70 and the diode section 80 may be the same as the longitudinal direction of each trench section described later.

The diode section 80 has an N+ type cathode region in a region that contacts the lower surface of the semiconductor substrate 10. In this specification, the region in which the cathode region is provided is referred to as the diode section 80. In other words, the diode section 80 is a region that overlaps with the cathode region when viewed from above. A P+ type collector region may be provided in a region other than the cathode region on the lower surface of the semiconductor substrate 10. In this specification, the diode section 80 may also include an extension region 81 that extends the diode section 80 in the Y-axis direction to the gate wiring described below. A collector region is provided on the lower surface of the extension region 81.

The transistor section 70 has a P+ type collector region in a region that contacts the lower surface of the semiconductor substrate 10. The transistor section 70 also has a gate structure that has an N type emitter region, a P type base region, a gate conductive portion, and a gate insulating film periodically arranged on the upper surface side of the semiconductor substrate 10.

The semiconductor device 100 may have one or more pads above the semiconductor substrate 10. The semiconductor device 100 of this example has a gate pad 164. The semiconductor device 100 may also have pads such as an anode pad, a cathode pad, and a current detection pad. Each pad is disposed near the edge 102. The vicinity of the edge 102 refers to the region between the edge 102 and the emitter electrode in a top view. When the semiconductor device 100 is mounted, each pad may be connected to an external circuit via wiring such as a wire.

A gate potential is applied to the gate pad 164. The gate pad 164 is electrically connected to the conductive portion of the gate trench portion of the active portion 160. The semiconductor device 100 includes a gate wiring that connects the gate pad 164 and the gate trench portion. In FIG. 20, the gate wiring is hatched with diagonal lines.

The gate wiring in this example has a peripheral gate wiring 130 and an active side gate wiring 129. The peripheral gate wiring 130 is disposed between the active portion 160 and the edge 102 of the semiconductor substrate 10 in a top view. The peripheral gate wiring 130 in this example surrounds the active portion 160 in a top view. The area surrounded by the peripheral gate wiring 130 in a top view may be the active portion 160. The peripheral gate wiring 130 is also connected to a gate pad 164. The peripheral gate wiring 130 is disposed above the semiconductor substrate 10. The peripheral gate wiring 130 may be a metal wiring containing aluminum or the like.

The active side gate wiring 129 is provided in the active section 160. By providing the active side gate wiring 129 in the active section 160, the variation in wiring length from the gate pad 164 can be reduced for each region of the semiconductor substrate 10.

The active side gate wiring 129 is connected to the gate trench portion of the active portion 160. The active side gate wiring 129 is disposed above the semiconductor substrate 10. The active side gate wiring 129 may be a wiring formed of a semiconductor such as polysilicon doped with impurities.

The active side gate wiring 129 may be connected to the peripheral gate wiring 130. In this example, the active side gate wiring 129 is provided extending in the X-axis direction from one peripheral gate wiring 130 to the other peripheral gate wiring 130 at approximately the center in the Y-axis direction, so as to cross the active section 160. When the active section 160 is divided by the active side gate wiring 129, the transistor section 70 and the diode section 80 may be arranged alternately in the X-axis direction in each divided region.

The semiconductor device 100 may also include a temperature sensor (not shown) that is a PN junction diode formed of polysilicon or the like, and a current detector (not shown) that simulates the operation of a transistor section provided in the active section 160.

The semiconductor device 100 of this example includes an edge termination structure 90 between the active portion 160 and the edge 102. The edge termination structure 90 of this example is disposed between the peripheral gate wiring 130 and the edge 102. The edge termination structure 90 relieves electric field concentration on the upper surface side of the semiconductor substrate 10. The edge termination structure 90 has a plurality of guard rings 92. The guard rings 92 are P-type regions in contact with the upper surface of the semiconductor substrate 10. The guard rings 92 may surround the active portion 160 in a top view. The multiple guard rings 92 are disposed at a predetermined interval between the peripheral gate wiring 130 and the edge 102. The guard ring 92 disposed on the outer side may surround the guard ring 92 disposed one step inward. The outer side refers to the side closer to the edge 102, and the inner side refers to the side closer to the peripheral gate wiring 130. By providing multiple guard rings 92, the depletion layer on the upper surface side of the active section 160 can be extended outward, improving the breakdown voltage of the semiconductor device 100. The edge termination structure 90 may further include at least one of a field plate and a resurf that are provided in a ring shape surrounding the active section 160.

21 is an enlarged view of region A in FIG. 20. Region A includes the transistor section 70, the diode section 80, and the active side gate wiring 129. The semiconductor device 100 of this example includes a gate trench section 40, a dummy trench section 30, a well region 11, an emitter region 12, a base region 14, and a contact region 15 provided inside the upper surface side of the semiconductor substrate 10. The gate trench section 40 and the dummy trench section 30 are each an example of a trench section. The semiconductor device 100 of this example also includes an emitter electrode 52 and an active side gate wiring 129 provided above the upper surface of the semiconductor substrate 10. The emitter electrode 52 and the active side gate wiring 129 are provided separately from each other.

An interlayer insulating film is provided between the emitter electrode 52 and the active gate wiring 129 and the upper surface of the semiconductor substrate 10, but is omitted in FIG. 21. In this example, contact holes 54 are provided in the interlayer insulating film so as to penetrate the interlayer insulating film. In FIG. 21, each contact hole 54 is hatched with diagonal lines.

The emitter electrode 52 is provided above the gate trench portion 40, the dummy trench portion 30, the well region 11, the emitter region 12, the base region 14, and the contact region 15. The emitter electrode 52 contacts the emitter region 12, the contact region 15, and the base region 14 on the upper surface of the semiconductor substrate 10 through a contact hole 54. The emitter electrode 52 is also connected to a dummy conductive portion in the dummy trench portion 30 through a contact hole provided in the interlayer insulating film. The emitter electrode 52 may be connected to the dummy conductive portion of the dummy trench portion 30 at the tip of the dummy trench portion 30 in the Y-axis direction.

The active side gate wiring 129 is connected to the gate trench portion 40 through a contact hole provided in the interlayer insulating film. The active side gate wiring 129 may be connected to the gate conductive portion of the gate trench portion 40 at the tip portion 41 of the gate trench portion 40 in the Y-axis direction. The active side gate wiring 129 is not connected to the dummy conductive portion in the dummy trench portion 30.

The emitter electrode 52 is formed of a material containing metal. FIG. 21 shows the range in which the emitter electrode 52 is provided. For example, at least a portion of the emitter electrode 52 is formed of aluminum or an aluminum-silicon alloy, such as a metal alloy such as AlSi or AlSiCu. The emitter electrode 52 may have a barrier metal made of titanium or a titanium compound under the region made of aluminum or the like. Furthermore, the emitter electrode 52 may have a plug formed by embedding tungsten or the like in the contact hole so as to contact the barrier metal and aluminum or the like.

The well region 11 is provided so as to overlap with the active side gate wiring 129. The well region 11 is also provided so as to extend by a predetermined width to an area where it does not overlap with the active side gate wiring 129. In this example, the well region 11 is provided away from the end of the contact hole 54 in the Y-axis direction toward the active side gate wiring 129. The well region 11 is a region of a second conductivity type having a higher doping concentration than the base region 14. In this example, the base region 14 is P- type, and the well region 11 is P+ type.

The transistor section 70 and the diode section 80 each have multiple trench sections arranged in the arrangement direction. In the transistor section 70 of this example, one or more gate trench sections 40 and one or more dummy trench sections 30 are alternately provided along the arrangement direction. In the diode section 80 of this example, multiple dummy trench sections 30 are provided along the arrangement direction. In the diode section 80 of this example, no gate trench section 40 is provided.

The gate trench portion 40 in this example may have two straight line portions 39 (portions of the trench that are straight along the extension direction) that extend along an extension direction perpendicular to the arrangement direction, and a tip portion 41 that connects the two straight line portions 39. The extension direction in FIG. 21 is the Y-axis direction.

It is preferable that at least a portion of the tip 41 is curved when viewed from above. The tip 41 connects the ends of the two straight portions 39 in the Y-axis direction, thereby reducing electric field concentration at the ends of the straight portions 39.

In the transistor section 70, the dummy trench section 30 is provided between each straight line portion 39 of the gate trench section 40. One dummy trench section 30 may be provided between each straight line portion 39, or multiple dummy trench sections 30 may be provided. The dummy trench section 30 may have a straight line shape extending in the extension direction, and may have a straight line portion 29 and a tip portion 31, similar to the gate trench section 40. The semiconductor device 100 shown in FIG. 21 includes both a straight line dummy trench section 30 without a tip portion 31 and a dummy trench section 30 with a tip portion 31.

The diffusion depth of the well region 11 may be deeper than the depth of the gate trench portion 40 and the dummy trench portion 30. The ends of the gate trench portion 40 and the dummy trench portion 30 in the Y-axis direction are provided in the well region 11 when viewed from above. In other words, at the ends of each trench portion in the Y-axis direction, the bottoms of each trench portion in the depth direction are covered by the well region 11. This makes it possible to reduce electric field concentration at the bottoms of each trench portion.

Mesa portions are provided between each trench portion in the arrangement direction. The mesa portion refers to the region inside the semiconductor substrate 10 that is sandwiched between the trench portions. As an example, the upper end of the mesa portion is the upper surface of the semiconductor substrate 10. The depth position of the lower end of the mesa portion is the same as the depth position of the lower end of the trench portion. In this example, the mesa portion is provided on the upper surface of the semiconductor substrate 10, extending in the extension direction (Y-axis direction) along the trench. In this example, the transistor portion 70 is provided with a mesa portion 60, and the diode portion 80 is provided with a mesa portion 61. In this specification, when the term "mesa portion" is used, it refers to both the mesa portion 60 and the mesa portion 61.

A base region 14 is provided in each mesa portion. Of the base regions 14 exposed on the upper surface of the semiconductor substrate 10 in the mesa portion, the region closest to the active gate wiring 129 is referred to as the base region 14-e. In FIG. 21, the base region 14-e is shown at one end in the extension direction of each mesa portion, but the base region 14-e is also provided at the other end of each mesa portion. In each mesa portion, at least one of the emitter region 12 of the first conductivity type and the contact region 15 of the second conductivity type may be provided in the region sandwiched between the base regions 14-e in a top view. In this example, the emitter region 12 is N+ type, and the contact region 15 is P+ type. The emitter region 12 and the contact region 15 may be provided between the base region 14 and the upper surface of the semiconductor substrate 10 in the depth direction.

The mesa portion 60 of the transistor portion 70 has an emitter region 12 exposed on the upper surface of the semiconductor substrate 10. The emitter region 12 is provided in contact with the gate trench portion 40. The mesa portion 60 in contact with the gate trench portion 40 may have a contact region 15 exposed on the upper surface of the semiconductor substrate 10.

Each of the contact regions 15 and emitter regions 12 in the mesa portion 60 is provided from one trench portion to the other trench portion in the X-axis direction. As an example, the contact regions 15 and emitter regions 12 in the mesa portion 60 are alternately arranged along the extension direction of the trench portion (Y-axis direction).

In another example, the contact region 15 and emitter region 12 of the mesa portion 60 may be provided in a stripe shape along the extension direction (Y-axis direction) of the trench portion. For example, the emitter region 12 is provided in a region that contacts the trench portion, and the contact region 15 is provided in a region sandwiched between the emitter regions 12.

The mesa portion 61 of the diode portion 80 does not have an emitter region 12. A base region 14 and a contact region 15 may be provided on the upper surface of the mesa portion 61. In the region sandwiched between the base regions 14-e on the upper surface of the mesa portion 61, a contact region 15 may be provided in contact with each of the base regions 14-e. In the region sandwiched between the contact regions 15 on the upper surface of the mesa portion 61, a base region 14 may be provided. The base region 14 may be disposed in the entire region sandwiched between the contact regions 15.

A contact hole 54 is provided above each mesa portion. The contact hole 54 is located in a region sandwiched between the base regions 14-e. In this example, the contact holes 54 are provided above the contact region 15, the base region 14, and the emitter region 12. The contact holes 54 are not provided in the regions corresponding to the base region 14-e and the well region 11. The contact holes 54 may be located in the center of the arrangement direction (X-axis direction) of the mesa portions 60.

In the diode section 80, an N+ type cathode region 82 is provided in a region adjacent to the underside of the semiconductor substrate 10. In the region of the underside of the semiconductor substrate 10 where the cathode region 82 is not provided, a P+ type collector region 22 may be provided. In FIG. 21, the boundary between the cathode region 82 and the collector region 22 is indicated by a dotted line.

The cathode region 82 is disposed away from the well region 11 in the Y-axis direction. This ensures a distance between the P-type region (well region 11) that has a relatively high doping concentration and is formed deep, and the cathode region 82, improving the breakdown voltage. In this example, the end of the cathode region 82 in the Y-axis direction is disposed farther from the well region 11 than the end of the contact hole 54 in the Y-axis direction. In another example, the end of the cathode region 82 in the Y-axis direction may be disposed between the well region 11 and the contact hole 54.

Figure 22A is a diagram showing an example of the b-b cross section in Figure 21. The b-b cross section is an XZ plane passing through the emitter region 12 and the cathode region 82. In this cross section, the semiconductor device 100 of this example has a semiconductor substrate 10, an interlayer insulating film 38, an emitter electrode 52, and a collector electrode 24. The interlayer insulating film 38 is provided on the upper surface of the semiconductor substrate 10. The interlayer insulating film 38 is a film that includes at least one layer of an insulating film such as silicate glass doped with impurities such as boron or phosphorus, a thermal oxide film, and other insulating films. The interlayer insulating film 38 is provided with the contact hole 54 described in Figure 21.

The emitter electrode 52 is provided above the interlayer insulating film 38. The emitter electrode 52 is in contact with the upper surface 21 of the semiconductor substrate 10 through a contact hole 54 in the interlayer insulating film 38. The collector electrode 24 is provided on the lower surface 23 of the semiconductor substrate 10. The emitter electrode 52 and the collector electrode 24 are made of a metal material such as aluminum. In this specification, the direction connecting the emitter electrode 52 and the collector electrode 24 (the Z-axis direction) is referred to as the depth direction.

The semiconductor substrate 10 has an N-type drift region 19. In this example, the drift region 19 is an N-type region extending from the lower end of the accumulation region 16 to the upper end of the buffer region 20. In this example, the drift region 19 has the high concentration region 150 described in FIG. 1 to FIG. 19. In FIG. 22A, the high concentration region 150 is hatched with diagonal lines. The high concentration region 150 may be provided in the transistor section 70, may be provided in the diode section 80, or may be provided in both the transistor section 70 and the diode section 80. The high concentration region 150 is a region provided from the upper end of the buffer region 20 toward the upper surface 21. An impurity chemical concentration peak 141 (see FIG. 1, etc.) is located at the upper end portion of the high concentration region 150.

The drift region 19 may have an N-type bulk donor region 18. The bulk donor region 18 is a region whose doping concentration matches the donor concentration of the bulk donor. The bulk donor region 18 is a region located above the high concentration region 150. In this example, the bulk donor region 18 is provided in each of the transistor portion 70 and the diode portion 80.

In the mesa portion 60 of the transistor section 70, an N+ type emitter region 12 and a P- type base region 14 are provided in this order from the upper surface 21 side of the semiconductor substrate 10. A bulk donor region 18 is provided below the base region 14. An N+ type accumulation region 16 may be provided in the mesa portion 60. The accumulation region 16 is disposed between the base region 14 and the bulk donor region 18.

The emitter region 12 is exposed on the upper surface 21 of the semiconductor substrate 10 and is in contact with the gate trench portion 40. The emitter region 12 may be in contact with the trench portions on both sides of the mesa portion 60. The emitter region 12 has a higher doping concentration than the bulk donor region 18.

The base region 14 is provided below the emitter region 12. In this example, the base region 14 is provided in contact with the emitter region 12. The base region 14 may be in contact with the trench portions on both sides of the mesa portion 60.

The accumulation region 16 is provided below the base region 14. The accumulation region 16 is an N+ type region with a higher doping concentration than the drift region 19. The accumulation region 16 may have a higher doping concentration than the high concentration region 150. By providing the high concentration accumulation region 16 between the drift region 19 and the base region 14, the carrier injection enhancement effect (IE effect) can be enhanced and the on-voltage can be reduced. The accumulation region 16 may be provided so as to cover the entire lower surface of the base region 14 in each mesa portion 60.

The mesa portion 61 of the diode section 80 has a P-type base region 14 in contact with the upper surface 21 of the semiconductor substrate 10. A bulk donor region 18 is provided below the base region 14. In the mesa portion 61, an accumulation region 16 may be provided below the base region 14.

In each of the transistor section 70 and the diode section 80, an N+ type buffer region 20 is provided on the lower surface 23 side of the high concentration region 150. The structure of the buffer region 20 is the same as the buffer region 20 described in Figures 1 to 19. The buffer region 20 may function as a field stop layer that prevents the depletion layer spreading from the lower end of the base region 14 from reaching the P+ type collector region 22 and the N+ type cathode region 82.

In the transistor portion 70, a P+ type collector region 22 is provided below the buffer region 20. The collector region 22 is an example of the underside region 201 described in FIG. 1 to FIG. 19. The acceptor concentration of the collector region 22 is higher than the acceptor concentration of the base region 14. The collector region 22 may contain the same acceptor as the base region 14, or may contain a different acceptor. The acceptor of the collector region 22 is, for example, boron.

In the diode section 80, an N+ type cathode region 82 is provided under the buffer region 20. The cathode region 82 is an example of the lower surface region 201 described in FIG. 1 to FIG. 19. The donor concentration of the cathode region 82 is higher than the donor concentration of the high concentration region 150. The donor of the cathode region 82 is, for example, hydrogen or phosphorus. The elements that become the donor and acceptor of each region are not limited to the above-mentioned examples. The collector region 22 and the cathode region 82 are exposed to the lower surface 23 of the semiconductor substrate 10 and are connected to the collector electrode 24. The collector electrode 24 may be in contact with the entire lower surface 23 of the semiconductor substrate 10. The emitter electrode 52 and the collector electrode 24 are formed of a metal material such as aluminum.

At least one gate trench portion 40 and at least one dummy trench portion 30 are provided on the upper surface 21 side of the semiconductor substrate 10. Each trench portion passes through the base region 14 from the upper surface 21 of the semiconductor substrate 10 to reach the drift region 19. In the region where at least one of the emitter region 12, the contact region 15, and the accumulation region 16 is provided, each trench portion also passes through these doped regions to reach the bulk donor region 18. The trench portion passing through the doped region is not limited to being manufactured in the order of forming the doped region and then the trench portion. The trench portion passing through the doped region also includes a trench portion formed after the trench portion is formed.

As described above, the transistor section 70 has a gate trench section 40 and a dummy trench section 30. The diode section 80 has a dummy trench section 30, but does not have a gate trench section 40. In this example, the boundary between the diode section 80 and the transistor section 70 in the X-axis direction is the boundary between the cathode region 82 and the collector region 22.

The gate trench portion 40 has a gate trench provided on the upper surface 21 of the semiconductor substrate 10, a gate insulating film 42, and a gate conductive portion 44. The gate insulating film 42 is provided to cover the inner wall of the gate trench. The gate insulating film 42 may be formed by oxidizing or nitriding the semiconductor on the inner wall of the gate trench. The gate conductive portion 44 is provided inside the gate insulating film 42 inside the gate trench. In other words, the gate insulating film 42 insulates the gate conductive portion 44 from the semiconductor substrate 10. The gate conductive portion 44 is formed of a conductive material such as polysilicon.

The gate conductive portion 44 may be provided longer than the base region 14 in the depth direction. The gate trench portion 40 in this cross section is covered by an interlayer insulating film 38 on the upper surface 21 of the semiconductor substrate 10. The gate conductive portion 44 is electrically connected to the gate wiring. When a predetermined gate voltage is applied to the gate conductive portion 44, a channel is formed by an electron inversion layer in the surface layer of the interface of the base region 14 that contacts the gate trench portion 40.

The dummy trench portion 30 may have the same structure as the gate trench portion 40 in the cross section. The dummy trench portion 30 has a dummy trench, a dummy insulating film 32, and a dummy conductive portion 34 provided on the upper surface 21 of the semiconductor substrate 10. The dummy conductive portion 34 may be connected to an electrode different from the gate pad. For example, the dummy conductive portion 34 may be connected to a dummy pad (not shown) that is connected to an external circuit different from the gate pad, and may be controlled differently from the gate conductive portion 44. The dummy conductive portion 34 may also be electrically connected to the emitter electrode 52. The dummy insulating film 32 is provided to cover the inner wall of the dummy trench. The dummy conductive portion 34 is provided inside the dummy trench and is provided on the inside of the dummy insulating film 32. The dummy insulating film 32 insulates the dummy conductive portion 34 from the semiconductor substrate 10. The dummy conductive portion 34 may be formed of the same material as the gate conductive portion 44. For example, the dummy conductive portion 34 is formed of a conductive material such as polysilicon. The dummy conductive portion 34 may have the same length in the depth direction as the gate conductive portion 44.

In this example, the gate trench portion 40 and the dummy trench portion 30 are covered by an interlayer insulating film 38 on the upper surface 21 of the semiconductor substrate 10. The bottoms of the dummy trench portion 30 and the gate trench portion 40 may be curved and convex downward (curved in cross section).

The semiconductor substrate 10 has distributions of the impurity chemical concentration C _I , the hydrogen chemical concentration C _H , and the doping concentration D _d similar to any of the examples described in Figures 1 to 19. According to the semiconductor device 100 of this example, by providing the high concentration region 150, the variation in the doping concentration in the drift region 19 can be suppressed.

FIG. 22B is a diagram showing an example of the distribution of the doping concentration D _d along the line d-d in FIG. 22A. The line d-d is a line parallel to the Z-axis passing through the collector region 22 and the mesa portion 60. The distribution of the doping concentration D _d in this example is similar to the distribution of the doping concentration D _d shown in FIG. 2 from the collector region 22 to the doping concentration peak 121. The doping concentration D _d in this example has a concentration peak in each of the accumulation region 16, the base region 14, and the emitter region 12. The semiconductor substrate 10 in this example has a bulk donor region 18 between the accumulation region 16 and the doping concentration peak 121. The bulk donor region 18 may be in contact with the accumulation region 16. That is, at the boundary between the bulk donor region 18 and the accumulation region 16, the doping concentration D _d may increase continuously from the bulk donor concentration D _b to the apex of the concentration peak of the accumulation region 16.

Figure 23 is a diagram showing another example of the b-b cross section in Figure 21. The semiconductor device 100 of this example differs from the example of Figure 22A in that the high concentration region 150 is provided throughout the entire drift region 19. The other structures may be the same as those of the example of Figure 22A.

In this example, the high concentration region 150 may be provided from the upper end of the buffer region 20 to a position where it contacts the accumulation region 16. The high concentration region 150 may be formed up to the inside of the accumulation region 16. In this case, the doping concentration peak 121 may be located in the accumulation region 16. If the semiconductor device 100 does not have the accumulation region 16, the high concentration region 150 may be provided up to a position where it contacts the base region 14. According to this example, the variation in doping concentration can be suppressed throughout the entire drift region 19.

The present invention has been described above using an embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

The order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before" or "prior to," and it should be noted that the processes may be performed in any order, unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is necessary to perform the processes in this order.

10: semiconductor substrate, 11: well region, 12: emitter region, 14: base region, 15: contact region, 16: accumulation region, 18: bulk donor region, 19: drift region, 20: buffer region, 21: upper surface, 22: collector region, 23: lower surface, 24: collector electrode, 29: straight portion, 30: dummy trench portion, 31: tip portion, 32: dummy insulating film, 34: dummy conductive portion, 38: interlayer insulating film, 39: straight portion, 40: gate trench portion, 41: tip portion, 42: gate insulating film, 44: gate conductive portion, 52: emitter electrode, 54: contact hole, 60, 61: mesa portion, 70: transistor portion, 80: diode portion, 81: extension region, 82: cathode region, 90: edge termination structure portion, 92: guard ring, 100: semiconductor device, 102: Edge, 106...passing region, 111...doping concentration peak, 112...lower side skirt, 113...upper side skirt, 114...slope, 121...doping concentration peak, 122...lower side skirt, 123...upper side skirt, 124...slope, 125...slope, 129...active side gate wiring, 130...peripheral gate wiring, 131...hydrogen chemical concentration peak, 132...lower side skirt, 133...upper side skirt, 134...slope, 141...impurity Chemical concentration peak, 142...lower tail, 143...upper tail, 144...slope, 145...slope, 150...high concentration region, 160...active part, 164...gate pad, 171...chemical concentration peak, 181...low concentration region, 201...lower surface region, 211...first defect density peak, 212...second defect density peak, 213...defect density peak, 311...upper limit, 312...lower limit, 313...upper limit, 314...lower limit

Claims (15)

a semiconductor substrate having a top surface and a bottom surface and including a bulk donor;
a buffer region of a first conductivity type disposed on the lower surface side of the semiconductor substrate and having one or more doping concentration peaks in a depth direction of the semiconductor substrate;
a high concentration region of a first conductivity type, the high concentration region having a donor concentration higher than a bulk donor concentration, disposed between the buffer region and the top surface of the semiconductor substrate;
Among the doping concentration peaks in the buffer region, a shallowest doping concentration peak closest to the bottom surface of the semiconductor substrate is a concentration peak of a hydrogen donor having a higher concentration than the other doping concentration peaks;
The ratio β between the actual bulk donor concentration N _Bre (/cm ³ ) and the specified bulk donor concentration value N _B0 (/cm ³ ) is defined by the following formula:
β=N _Bre /N _B0
The ratio γ of the actual donor concentration N _Fre (/cm ³ ) in the high-concentration region to the target value N _F0 (/cm ³ ) of the donor concentration in the high-concentration region is defined by the following formula:
γ=N _Fre /N _F0
A parameter ε′, which means that the specification value N _B0 of the bulk donor concentration is set to be smaller than the target value N _F0 of the donor concentration by ε′, is defined by the following equation:
N _B0 = ε ' × N _F0
The relationship between the ratio β, the ratio γ, and the parameter ε′ is expressed by the following formula:
γ=1+ε′(β−1)
In the above formula, the value of the ratio β is 0.1 or more and 10 or less, the value of the ratio γ is 0.85 or more and 1.15 or less, and the value of the parameter ε′ is 0.001 or more and 0.5 or less,
A semiconductor device, wherein the ratio γ satisfies the above formula within the ranges of the ratio β, the ratio γ, and the parameter ε'. The semiconductor device according to claim 1 , wherein the semiconductor substrate is an MCZ substrate. 3. The semiconductor device according to claim 1, wherein the actual donor concentration N _Fre at the center in the depth direction of the semiconductor substrate is equal to or greater than (9.20245×10 ¹⁵ )/x and is equal to or greater than (9.20245×10 ¹⁶ )/x, where x (V) is a rated voltage of the semiconductor device. 4. The semiconductor device according to claim 1, wherein the actual bulk donor concentration N _Bre is equal to or greater than (9.20245×10 ¹² )/x and equal to or less than (4.60123×10 ¹⁶ )/x, where x (V) is a rated voltage of the semiconductor device. an impurity chemical concentration peak disposed on the top surface side of the semiconductor substrate;
the high concentration region includes a uniform region having a uniform doping concentration;
The doping concentration distribution of the uniform region has a value within ±50% of an average concentration of the doping concentration distribution in a first range,
5. The semiconductor device according to claim 1, wherein the first range is a section having a length of _0.5ZL including a center _Z12c between the shallowest doping concentration peak and the impurity chemical concentration peak, where _ZL is a length of the high concentration region in the depth direction, and _Z12c is a center between the shallowest doping concentration peak and the impurity chemical concentration peak in the depth direction. an impurity chemical concentration peak disposed on the top surface side of the semiconductor substrate;
5. The semiconductor device according to claim 1, wherein an upper side base where the impurity chemical concentration decreases from the apex of the impurity chemical concentration peak toward the upper surface side decreases more steeply than a lower side base where the impurity chemical concentration decreases from the apex of the impurity chemical concentration peak toward the lower surface side. The semiconductor device according to claim 1 , wherein the buffer region has two or more of the doping concentration peaks. determining a specification value N _B0 (/cm ³ ) for the bulk donor concentration of the semiconductor substrate;
determining a target value N _F0 (/cm ³ ) of a donor concentration of the semiconductor substrate;
a first implantation step of implanting charged particles and hydrogen ions from an upper surface or a lower surface of the semiconductor substrate;
a first annealing step of annealing the semiconductor substrate;
Equipped with
The hydrogen donor concentration by the implantation of hydrogen ions is N _H (/cm ³ ),
The actual bulk donor concentration of the semiconductor substrate is N _Bre (/cm ³ );
If the final donor concentration actually obtained in the semiconductor substrate is N _Fre (/cm ³ ), then:
The target value N _F0 of the donor concentration is expressed by N _F0 =N _H +N _B0 , where N _B0 is the specification value of the bulk donor concentration and N _H is the hydrogen donor concentration,
The final donor concentration N _Fre is expressed by N _Fre = N _H + N _Bre , where N _Bre is the actual bulk donor concentration and N _Bre is the hydrogen donor concentration;
The ratio β between the actual bulk donor concentration N _Bre and the specified bulk donor concentration N _B0 is defined as follows:
β=N _Bre /N _B0
The ratio γ between the actual donor concentration N _Fre and the target value N _F0 of the donor concentration is defined by the following formula:
γ=N _Fre /N _F0
A parameter ε′, which means that the specification value N _B0 of the bulk donor concentration is set to be smaller than the target value N _F0 of the donor concentration by ε′, is defined by the following equation:
N _B0 = ε ' × N _F0
The relationship between the ratio β, the ratio γ, and the parameter ε′ is expressed by the following formula:
γ=1+ε′(β−1)
In the above formula, the value of the ratio β is 0.1 or more and 10 or less, the value of the ratio γ is 0.85 or more and 1.15 or less, and the value of the parameter ε′ is 0.001 or more and 0.5 or less,
the first implantation step and the first annealing step are performed within ranges of the ratio β, the ratio γ, and the parameter ε' so that the ratio γ satisfies the above formula. The method for manufacturing a semiconductor device according to claim 8 , wherein the semiconductor substrate is an MCZ substrate. 10. The method for manufacturing a semiconductor device according to claim 8, wherein, when a rated voltage of the semiconductor device is x (V), the final donor concentration N _Fre at the center in the depth direction of the semiconductor substrate is equal to or greater than (9.20245×10 ¹⁵ )/x and is equal to or greater than (9.20245×10 ¹⁶ )/x. 11. The method for manufacturing a semiconductor device according to claim 8, wherein the actual bulk donor concentration N _Bre is equal to or greater than (9.20245×10 ¹² )/x and equal to or less than (4.60123×10 ¹⁶ )/x, where x (V) is a rated voltage of the semiconductor device. 12. The method for manufacturing a semiconductor device according to claim 8, wherein in the first implantation step, the hydrogen ions are implanted from the lower surface to a first position, and the charged particles are implanted to a second position closer to the upper surface of the semiconductor substrate than the first position. The method for manufacturing a semiconductor device according to claim 12 , wherein the second position is disposed on the top surface side of the semiconductor substrate. 14. The method for manufacturing a semiconductor device according to claim 12, wherein in the first annealing step, a high concentration region having a donor concentration higher than the bulk donor concentration is formed in the semiconductor substrate from the first position to the second position. the high concentration region includes a uniform region having a uniform doping concentration;
The doping concentration distribution of the uniform region has a value within ±50% of an average concentration of the doping concentration distribution in a first range,
15. The method for manufacturing a semiconductor device according to claim 14, wherein when a length of the high concentration region in a depth direction is _ZL and a center between the first position and the second position in the depth direction is _Z12c , the first range is a section having a length of _0.5ZL including a center _Z12c .

Images